Internet Draft S. Farrell (SSE) PKIX Working Group C. Adams (Nortel) draft-ietf-pkix-ipki3cmp-01.txt Expires in 6 months December 1996 Internet Public Key Infrastructure Part III: Certificate Management Protocols Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of 6 months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za(Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract This is the fourth draft of the Internet Public Key Infrastructure X.509 Certificate Management Protocols. This version builds on draft-ietf- pkix-ipki3cmp-01.txt and discussions on the PKIX mailing list (ietf- pkix@tandem.com) and at the Montreal IETF meeting (June 1996). Summary of changes since the third draft: - New messages defined to ask for general information from a PKI management entity (RA/CA). - New fields added allowing for: proof of possession of a private key; request for publication of a certificate; and request for archival of a private key. - ASN.1 simplifications. - First concrete definition of what is mandatory for conformance. - File- and socket-based protocols defined. 1. Introduction The layout of this draft is as follows: - Section 1 contains an overview of PKI management Farrell, Adams [Page 1] INTERNET-DRAFT December 1996 - Section 2 contains discussion of assumptions and restrictions - Section 3 contains data structures used for PKI management messages - Section 4 defines the functions which are to be carried out in PKI management including those which must be supported by conforming implementations and those which are optional - Section 5 describes a simple protocol for transporting PKI messages 1.1 PKI Management Overview The PKI must be structured to be consistent with the types of individuals who must administer it. Providing such administrators with unbounded choices not only complicates the software required but also increases the chances that a subtle mistake by an administrator or software developer will result in broader compromise. Similarly, restricting administrators with cumbersome mechanisms will cause them not to use the PKI. Management protocols are required to support on-line interactions between Public Key Infrastructure (PKI) components. For example, a management protocol might be used between a CA and a client system with which a key pair is associated, or between two CAs which cross-certify each other. 2.1 PKI Management Model Before specifying particular message formats and procedures we first define the entities involved in PKI management and their interactions (in terms of the PKI management functions required). We then group these functions in order to accommodate different identifiable types of end entities. 1.2 Definitions of PKI Entities The entities involved in PKI management include the end entity (i.e. the entity to be named in the subject field of a certificate) and the certification authority (i.e. the entity named in the issuer field of a certificate). A registration authority may also be involved in PKI management. 1.2.1 Subjects and End Entities The term "subject" is used here to refer to the entity named by the subject field of a certificate; when we wish to distinguish the tools and/or software used by the subject (e.g. a local certificate management module) we will use the term "subject equipment". In general, we prefer the term "end entity" rather than subject in order to avoid confusion with the field name. It is important to note that the end entities here will include not only human users of applications, but also applications themselves (e.g. for IP security). This factor influences the protocols which the PKI management operations use; e.g., applications software is far more likely to know exactly which certificate extensions are required than Farrell, Adams [Page 2] INTERNET-DRAFT December 1996 are human users. PKI management entities are also end entities in the sense that they are sometimes named in the subject field of a certificate or cross-certificate. Where appropriate, the term "end- entity" will be used to refer to end entities who are not PKI management entities. All end entities require secure local access to some information -- at a minimum, their own name and private key, the name of a CA which is directly trusted by this subject and that CA's public key (or a fingerprint of the public key where a self-certified version is available elsewhere). Implementations may use secure local storage for more than this minimum (e.g. the end entity's own certificate or application-specific information). The form of storage will also vary -- from files to tamper resistant cryptographic tokens. Such local trusted storage is referred to here as the end entity's Personal Security Environment (PSE). Though PSE formats are out of scope of this document (they are very dependent on equipment, et cetera), a generic interchange format for PSEs is defined here - a certification response message may be used. 1.2.2 Certification Authority The certification authority (CA) may or may not actually be a real "third party" from the end entity's point of view. Quite often, the CA will actually belong to the same organisation as the end entities it supports. Again, we use the term CA to refer to the entity named in the issuer field of a certificate; when it is necessary to distinguish the software or hardware tools used by the CA we use the term "CA equipment". The CA equipment will often include both an "off-line" component and an "on-line" component, with the CA private key only available to the "off- line" component. This is, however, a matter for implementers (though it is also relevant as a policy issue). We use the term "root CA" to indicate a CA which is directly trusted by an end entity, that is, securely acquiring the value of a root CA public key requires some out-of-band step(s). This term does not indicate that a root CA is at the top of any hierarchy, simply that the CA in question is trusted directly. A subordinate CA is one which is not a root CA for the end entity in question. Often, a subordinate CA will not be a root CA for any entity but this is not mandatory. 1.2.3 Registration Authority In addition to end entities and CAs, many environments call for the existence of a registration authority (RA) separate from the certification authority. The functions which the registration authority may carry out will vary from case to case but may include personal authentication, token distribution, revocation reporting, name assignment, key generation, archival of key pairs, et cetera. Farrell, Adams [Page 3] INTERNET-DRAFT December 1996 This document views the RA as an optional component - when it is not present the CA is assumed to be able to carry out the RA's functions so that the PKI management protocols are the same from the end entity's point of view. Again, we distinguish, where necessary, between the RA and the tools used (the "RA equipment"). Note that an RA is itself an end entity. We further assume that all RAs are in fact certified end entities and that RA private keys are usable for signing. How a particular CA equipment identifies some end entities as RAs is an implementation issue (so there is no special RA certification operation). We do not mandate that the RA is certified by the CA with which it is interacting at the moment (so one RA may work with more than one CA whilst only being certified once). In some circumstances end entities will communicate directly with a CA even where an RA is present. For example, for initial registration and/or certification the subject may use its RA, but communicate directly with the CA in order to refresh its certificate. 1.3 PKI Management Requirements The protocols given here meet the following requirements on PKI management. 1. PKI management must conform to ISO 9594-8 and the associated amendments (certificate extensions) 2. PKI management must conform to the other parts of this series. 3. It must be possible to regularly update any key pair without affecting any other key pair. 4. The use of confidentiality in PKI management protocols must be kept to a minimum in order to ease regulatory problems. 5. PKI management protocols must allow the use of different industry- standard cryptographic algorithms, (specifically including, RSA, DSA, MD5, SHA-1) -- this means that any given CA, RA, or end entity may, in principal, use whichever algorithms suit it for its own key pair(s). 6. PKI management protocols must not preclude the generation of key pairs by the end entity concerned, by an RA, or by a CA -- key generation may also occur elsewhere, but for the purposes of PKI management we can regard key generation as occurring wherever the key is first present at an end entity, RA or CA. 7. PKI management protocols must support the publication of certificates by the end entity concerned, by an RA or by a CA. Different implementations and different environments may choose any of the above Farrell, Adams [Page 4] INTERNET-DRAFT December 1996 approaches. 8. PKI management protocols must support the production of CRLs by allowing certified end entities to make requests for the revocation of certificates - this must be done in such a way that the denial-of- service attacks which are possible are not made simpler. 9. PKI management protocols must be usable over a variety of "transport" mechanisms, specifically including mail, http, TCP/IP and ftp. 10. Final authority for certification creation rests with the CA; no RA or end entity equipment should assume that any certificate issued by a CA will contain what was requested -- a CA may alter certificate field values or may add, delete or alter extensions according to its operating policy; the only exception to this is the public key, which the CA may not modify (assuming that the CA was presented with the public key value). In other words, all PKI entities (end entities, RAs and CAs) must be capable of handling responses to requests for certificates in which the actual certificate issued is different from that requested -- for example, a CA may shorten the validity period requested. 11. A graceful, scheduled change-over from one non-compromised CA key pair to the next must be supported (CA key update). An end-entity whose PSE contains the new CA public key (following a CA key update) must also be able to verify certificates verifiable using the old public key. End entities who directly trust the old CA key pair must also be able to verify certificates signed using the new CA private key. (Required for situations where the old CA public key is "hardwired" into the end entity's cryptographic equipment). 12. The Functions of an RA may, in some implementations or environments, be carried out by the CA itself. The protocols must be designed so that end entities will use the same protocol regardless of whether the communication is with an RA or CA. 1.4 13. Where an end entity requests a certificate containing a given public key value, the end entity must show the ability to use the corresponding private key value. This is accomplished in various ways, depending on the type of certification request. See the section "Proof of Possession of Private Key" for details. 1.5 PKI Management Operations The following diagram shows the relationship between the entities defined above in terms of the PKI management operations. The letters in the diagram indicate "protocols" in the sense that a defined set of PKI management messages can be sent along each of the lettered lines. cert. publish +------------+ +---+ +------------ | End Entity | Operations | C | | g +------------+ | e | <--------+ | ^ initial | r | a | | b registration/ Farrell, Adams [Page 5] INTERNET-DRAFT December 1996 | t | PKI "users" | | certification | | | | key pair recovery | / | | | key pair update | | | | certificate update | C | V | revocation request | R | -------+-+-----+-+------+-+----- | L | PKI management | ^ | ^ | | entities a | | b a | | b | | V | | | | R | g +------+ d | | | e | <------------ | RA | <-----+ | | | p | cert. | | ----+ | | | | o | publish +------+ c | | | | | s | | | | | | i | V | V | | t | h +------------+ i | o | <------------------------| CA |-------> | r | +------------+ "out-of-band" | y | cert. publish | ^ publication | | CRL publish | | +---+ | | cross-certification e | | f cross-certificate | | update | | V | +------+ | CA-2 | +------+ Figure 1 - PKI Entities At a high level the set of operations for which management messages are defined can be grouped as follows. 1 CA establishment: When establishing a new CA, certain steps are required (e.g., production of initial CRLs, export of CA public key). 2 End entity initialisation: this includes importing a CA public key and requesting information about the options supported by a PKI management entity. 3 Certification: various operations result in the creation of new certificates: 3.1 initial registration/certification: This is the process whereby a subject first makes itself known to a CA or RA, prior to the CA issuing a certificate or certificates for that user. The end result of this process (when it is successful) is that a CA issues a certificate for an end entity's public key, and returns that certificate to the subject and/or posts that certificate in a public repository. This process may, and typically will, involve multiple "steps", possibly including an initialization of the end entity's equipment. For example, the subject 3.2 Farrell, Adams [Page 6] INTERNET-DRAFT December 1996 1.1 equipment must be securely initialized with the public key of a CA, to be used in validating certificate paths. Furthermore, a subject typically needs to be initialized with its own key pair(s). 1.2 key pair update: Every key pair needs to be updated regularly (i.e., replaced with a new key pair), and a new certificate needs to be issued. 1.3 certificate update: As certificates expire they may be "refreshed" if nothing relevant in the environment has changed. 1.4 CA key pair update: As with end entities, CA key pairs need to be updated regularly; however, different mechanisms are required. 1.5 cross-certification: Two CAs exchange the information necessary to establish cross-certificates between those CAs. 1.6 cross-certificate update: Similar to a normal certificate update but involving a cross-certificate. 2 Certificate/CRL discovery operations: some PKI management operations result in the publication of certificates or CRLs 2.1 certificate publication: Having gone to the trouble of producing a certificate some means for publishing it is needed. 2.2 CRL publication: As for certificates. 3 Recovery operations: some PKI management operations are used when an end entity has "lost" it's PSE 3.1 key pair recovery: As an option, user client key materials (e.g., a user's private key used for decryption purposes) may be backed up by a CA, an RA or a key backup system associated with a CA or RA. If a subject needs to recover these backed up key materials (e.g., as a result of a forgotten password or a lost key chain file), a protocol exchange may be needed to support such recovery. 4 Revocation operations: some PKI operations result in the creation of new CRL entries and/or new CRLs 4.1 revocation request: An authorized person advises a CA of an abnormal situation requiring certificate revocation. 5 PSE operations: whilst the definition of PSE operations (e.g. moving a PSE, changing a PIN, etc.) are beyond the scope of this specification, we do define a PKIMessage which can form the basis of such operations. Note that on-line protocols are not the only way of implementing the above operations. For all operations there are off-line methods of achieving the same result, and this specification does not mandate use of on-line protocols. For example, when hardware tokens are used, many of the operations may be achieved as part of the physical token delivery. Later sections define a set of standard protocols supporting the above operations. The protocols for conveying these exchanges in different environments (file based, on-line, E-mail, and WWW) may also be specified. Farrell, Adams [Page 7] INTERNET-DRAFT December 1996 2. Assumptions and restrictions 2.1 End entity initialisation The first step for and end entity in dealing with PKI management entities is to request information about the PKI functions supported and optionally to securely acquire a copy of the relevant root CA public key(s). 2.2 Initial registration/certification There are many schemes which can be used to achieve initial registration and certification of end entities. No one method is suitable for all situations due to the range of policies which a CA may implement and the variation in the types of end entity which can occur. We can however, classify the initial registration / certification schemes which are supported by this specification. Note that the word "initial", above, is crucial - we are dealing with the situation where the end entity in question has had no previous contact with the PKI. Where the end entity already possesses certified keys then some simplifications are possible. Having classified the schemes which are supported by this specification we can then specify some as mandatory and some as optional. The goal is that the mandatory schemes cover a sufficient number of the cases which will arise in real use, whilst the optional schemes are available for special cases which arise less frequently. In this way we achieve a balance between flexibility and ease of implementation. We will now describe the classification of initial registration / certification schemes. 2.2.1 Criteria used 2.2.1.1 Initiation of registration / certification In terms of the PKI messages which are produced we can regard the initiation of the initial registration / certification exchanges as occurring wherever the first PKI message relating to the end entity is produced. Note that the real world initiation of the registration / certification procedure may occur elsewhere (e.g. a personnel department may telephone an RA operator). The possible locations are: at the end entity, an RA or a CA. 2.2.1.2 End entity message origin authentication The on-line messages produced by the end entity which requires a certificate may be authenticated or not. The requirement here is to authenticate the origin of any messages from the end entity to the PKI (CA/RA). In this specification, such authentication is achieved by the PKI (CA/RA) issuing the end entity with a secret value (initial authentication key) and reference value (used to identify the transaction) via some out-of-band means. The initial authentication key can then be used to protect relevant PKI messages. We can thus classify the initial registration/certification scheme Farrell, Adams [Page 8] INTERNET-DRAFT December 1996 according to whether or not the on-line end-entity -> PKI messages are authenticated or not. Note 1: We do not discuss the authentication of the PKI -> end entity messages here as this is always required. In any case, it can be achieved simply once the root-CA public key has been installed at the end entity's equipment or based on the initial authentication key. Note 2: An initial registration / certification procedure can be secure where the messages from the end entity are authenticated via some out- of-band means (e.g. a subsequent visit). 2.2.1.3 Location of key generation In this specification, key generation is regarded as occurring wherever either the public or private component of a key pair first occurs in a PKI message. Note that this does not preclude a centralised key generation service - the actual key pair may have been generated elsewhere and transported to the end entity, RA or CA. There are thus three possibilities for the location of key generation: the end-entity, an RA or a CA. 2.2.1.4 Confirmation of successful certification Following the creation of an initial certificate for an end entity, additional assurance can be gained by having the end entity explicitly confirm successful receipt of the message containing (or indicating the creation of) the certificate. Naturally, this confirmation message must be protected (based on the initial authentication key or other means). This gives two further possibilities: confirmed or not. 2.2.2 Mandatory schemes The criteria above allow for a large number of initial registration / certification schemes. This specification mandates that conforming RA/CA equipment must support both of the schemes listed below. Conforming end entity equipment must support one of the schemes listed below. 2.2.2.1 Centralised scheme In terms of the classification above, this scheme is where: - initiation occurs at the certifying CA; - no on-line message authentication is required; - key generation occurs at the certifying CA; - no confirmation message is required. In terms of message flow, this scheme means that the only message required is sent from the CA to the end entity. The message must contain the entire PSE for the end entity. Some out-of-band means must be provided to allow the end entity to authenticate the message received. 2.2.2.2 Basic authenticated scheme In terms of the classification above, this scheme is where: - initiation occurs at the end entity - message authentication is required - key generation occurs at the end entity - a confirmation message is required Farrell, Adams [Page 9] INTERNET-DRAFT December 1996 In terms of message flow, the scheme is as follows: End entity CA ========== ============= out-of-band distribution of initial authentication key and reference value Key generation Creation of certification request Protect request with IAK -->>--certification request-->> verify request process request create response --<<--certification response--<<-- handle response create confirmation -->>--confirmation message-->>-- verify confirmation (Where verification of the confirmation message fails, the CA must revoke the newly issued certificate if necessary.) 2.3 Proof of Possession of Private Key In order to prevent certain attacks, the PKI management operations specified here require end-entities to prove that they have possession of (i.e., are able to use) the private key corresponding to the public key for which a certificate is requested. This is accomplished in a different ways, depending on the type of key for which a certificate is requested. If a key can be used for multiple purposes (e.g. an RSA key) then any of the methods may be used. This specification explicitly allows for cases where an end entity supplies the relevant proof to an RA and the RA subsequently attests to the CA that the required proof has been received (and validated!). For example, an end entity wishing to have a signing key certified could send the appropriate signature to the RA which then simply notifies the relevant CA that the end entity has supplied the required proof. Of course, such a situation may be disallowed by some policies. 2.3.1 Signature Keys For signature keys, the end-entity can sign a value to prove possession of the private key. 2.3.2 Encryption Keys For encryption keys, the end-entity can be required to decrypt a value in order to prove possession of the private key. This can be achieved either directly or indirectly. The direct method is to issue a random challenge to which an immediate response is required. The indirect method is to issue a certificate which is encrypted for the Farrell, Adams [Page 10] INTERNET-DRAFT December 1996 end entity (and have the end entity demonstrate its ability to decrypt this certificate in the confirmation message). This allows a CA to issue a certificate in a form which can only be used by the intended end entity. This specification uses the indirect method because this requires no extra messages to be sent (i.e., the proof can be demonstrated using the {request, response, confirmation} triple of messages). 2.3.3 Key Agreement Keys For key agreement keys, the end entity and the PKI management entity (i.e. CA or RA) must establish a shared secret key in order to prove that the end entity has possession of the private key. Note that this need not impose any restrictions on the keys which can be certified by a given CA -- in particular, for Diffie-Hellman keys the end entity may freely choose its algorithm parameters -- provided that the CA can generate a short-term (or one-time) key pair with the appropriate parameters when necessary. 2.4 Root CA key update This discussion only applies to CAs which are a root CA for some end entity. The basis of the procedure described here is that the CA protects its new public key using its previous private key and vice versa. Thus when a CA updates its key pair it must generate two new cACertificate attribute values if certificates are made available using an X.500 directory. When a CA changes its key pair those entities who have acquired the old CA public key via "out-of-band" means are most affected. It is these end entities who will need access to the new CA public key protected with the old CA private key. However, they will only require this for a limited period (until they have acquired the new CA public key via the "out-of-band" mechanism). This will typically be easily achieved when these end entity's certificates expire. The data structure used to protect the new and old CA public keys is a standard certificate (which may also contain extensions). There are no new data structures required. Notes: 1.This scheme does not make use of any of the X.509 v3 extensions as it should be able to work even for version 1 certificates. The presence of the KeyIdentifier extension would make for efficiency improvements. 2.While the scheme could be generalized to cover cases where the CA updates its key pair more than once during the validity period of one of its end entity's certificates, this generalization seems of dubious value. This means that the validity period of a CA key pair must be Farrell, Adams [Page 11] INTERNET-DRAFT December 1996 greater than the validity period of any certificate issued by that CA using that key pair. 3.This scheme forces end entities to acquire the new CA public key on the expiry of the last certificate they owned which was signed with the old CA private key (via the "out-of-band" means). Certificate and/or key update operations occurring at other times do not necessarily require this (depending on the end entity's equipment). 2.4.1 CA Operator actions To change the key of the CA, the CA operator does the following: 1.Generate a new key pair. 2.Create a certificate containing the old CA public key signed with the new private key (the "old with new" certificate). 3.Create a certificate containing the new CA public key signed with the old private key (the "new with old" certificate). 4.Create a certificate containing the new CA public key signed with the new private key (the "new with new" certificate). 5.Publish these new certificates via the directory and/or other means. (A CAKeyUpdAnn message.) 6.Export the new CA public key so that end entities may acquire it using the "out-of-band" mechanism. The old CA private key is then no longer required. The old CA public key will however remain in use for some time. The time when the old CA public key is no longer required (other than for non-repudiation) will be when all end entities of this CA have acquired the new CA public key via "out-of-band" means. The "old with new" certificate should have a validity period starting at the generation time of the old key pair and ending at the time at which the CA will next update its key pair. The "new with old" certificate should have a validity period starting at the generation time of the new key pair and ending at the time by which all end entities of this CA will securely possess the new CA public key. The "new with new" certificate should have a validity period starting at the generation time of the new key pair and ending at the time at which the CA will next update its key pair. 2.4.2 Verifying Certificates. Normally when verifying a signature the verifier simply(!) verifies the certificate containing the public key of the signer. However, once a CA is allowed to update its key there are a range of new possibilities. These are shown in the table below. Farrell, Adams [Page 12] INTERNET-DRAFT December 1996 Repository contains NEW Repository contains only OLD and OLD public keys public key (due to e.g. delay in publication) PSE PSE Contains PSE Contains PSE Contains Contains OLD public NEW public OLD public NEW public key key key key Signer's Case 1: Case 3: Case 5: Case 7: certifi- This is In this case Although the In this case cate is the the verifier CA operator the CA protected standard must access has not operator has using NEW case where the updated the not updated public the directory in directory the the directory key verifier order to get verifier can and so the can the value of verify the verification directly the NEW certificate will FAIL verify the public key directly - certificate this is thus without the same as using the case 1. directory Signer's Case 2: Case 4: Case 6: Case 8: certifi- In this In this case The verifier Although the cate is case the the verifier thinks this CA operator protected verifier can directly is the has not using OLD must verify the situation of updated the public access the certificate case 2 and directory the key directory without will access verifier can in order using the the verify the to get the directory directory, certificate value of however the directly - the OLD verification this is thus public key will FAIL the same as case 4. 2.4.2.1 Verification in cases 1, 4, 5 and 8. In these cases the verifier has a local copy of the CA public key which can be used to verify the certificate directly. This is the same as the situation where no key change has ever occurred. Note that case 8 may arise between the time when the CA operator has generated the new key pair and the time when the CA operator stores the updated attributes in the directory. Case 5 can only arise if the CA operator has issued both the signer's and verifier's certificates during this "gap" (the CA operator should avoid this as it leads to the failure cases described below). 2.4.2.2 Verification in case 2. In case 2 the verifier must get access to the old public key of the CA. The verifier does the following: Farrell, Adams [Page 13] INTERNET-DRAFT December 1996 1.Lookup the CACertificate attribute in the directory and pick the appropriate value (based on validity periods) 2.Verify that this is correct using the new CA key (which the verifier has locally). 3.If correct then check the signer's certificate using the old CA key. Case 2 will arise when the CA operator has issued the signer's certificate, then changed key and then issued the verifier's certificate, so it is quite a typical case. 2.4.2.3 Verification in case 3. In case 3 the verifier must get access to the new public key of the CA. The verifier does the following: 1.Lookup the CACertificate attribute in the directory and pick the appropriate value (based on validity periods). 2.Verify that this is correct using the old CA key (which the verifier has stored locally). 3.If correct then check the signer's certificate using the new CA key. Case 3 will arise when the CA operator has issued the verifier's certificate, then changed key and then issued the signer's certificate, so it is also quite a typical case. 2.4.2.4 Failure of verification in case 6. In this case the CA has issued the verifier's PSE containing the new key without updating the directory attributes. This means that the verifier has no means to get a trustworthy version of the CA's old key and so verification fails. Note that the failure is the CA operator's fault. 2.4.2.5 Failure of verification in case 7. In this case the CA has issued the signer's certificate protected with the new key without updating the directory attributes. This means that the verifier has no means to get a trustworthy version of the CA's new key and so verification fails. Note that the failure is again the CA operator's fault. 2.4.3 Revocation - Change of CA key As we saw above the verification of a certificate becomes more complex once the CA is allowed to change its key. This is also true for revocation checks as the CA may have signed the CRL using a newer private key than the one that is within the user's PSE. The analysis of the alternatives is as for certificate verification. 3. Data Structures This section contains descriptions of the data structures required for PKI management messages. Section 4 describes constraints on their values Farrell, Adams [Page 14] INTERNET-DRAFT December 1996 and the sequence of events for each of the various PKI management operations. Section 5 describes how these may be encapsulated in various transport mechanisms. 3.1 Overall PKI Message All of the messages used in PKI management use the following structure: PKIMessage ::= SEQUENCE { header PKIHeader, body PKIBody, protection [0] PKIProtection OPTIONAL, extraCerts [1] SEQUENCE OF Certificate OPTIONAL } The PKIHeader contains information which is common to many PKI messages. The PKIBody contains message-specific information. The PKIProtection contains bits which protect the PKI message. The extra certificates field can contain certificates which may be useful to the recipient. For example, this can be used by a CA or RA to present an end entity with certificates which it needs to verify it's own new certificate (if the CA that issued the end entity's certificate is not a root CA for the end entity). Note also that this field does not necessarily contain a certification path - the recipient may have to sort, select from, or otherwise process the extra certificates in order to use them. 3.1.1 PKI Message Header All PKI messages require some header information for addressing and transaction identification. Some of this information will also be present in a transport-specific envelope; however, if the PKI message is protected then this information is also protected (i.e. we make no assumption about secure transport). The following data structure is used to contain this information: PKIHeader ::= SEQUENCE { pvno INTEGER { ietf-version1 (0) }, sender GeneralName, -- identifies the sender recipient GeneralName, -- identifies the intended recipient messageTime [0] GeneralizedTime OPTIONAL, -- time of production of this message (used when sender -- believes that the transport will be "suitable"; i.e., -- that the time will still be meaningful upon receipt) protectionAlg [1] AlgorithmIdentifier OPTIONAL, -- algorithm used for calculation of protection bits senderKID [2] KeyIdentifier OPTIONAL, recipKID [3] KeyIdentifier OPTIONAL, Farrell, Adams [Page 15] INTERNET-DRAFT December 1996 -- to identify specific keys used for protection transactionID [4] OCTET STRING OPTIONAL, -- identifies the transaction, i.e. this will be the same in -- corresponding request, response and confirmation messages senderNonce [5] OCTET STRING OPTIONAL, recipNonce [6] OCTET STRING OPTIONAL, -- nonces used to provide replay protection, senderNonce -- is inserted by the creator of this message; recipNonce -- is a nonce previously inserted in a related message by -- the intended recipient of this message freeText [7] PKIFreeText OPTIONAL -- this may be used to indicate context-specific -- instructions (this field is intended for human -- consumption) } PKIFreeText ::= CHOICE { iA5String [0] IA5String, bMPString [1] BMPString } The pvno field is fixed for this version of IPKI. The sender field contains the name of the sender of the PKIMessage. This name (in conjunction with senderKID, if supplied) should be usable to verify the protection on the message. If nothing about the sender is known to the sending entity (e.g., in the InitReqContent message, where the end entity may not know its own DN, e-mail name, IP address, etc.), then the "sender" field must contain a "NULL" value; that is, the SEQUENCE OF relative distinguished names is of zero length. In such a case the senderKID field must hold an identifier (i.e., a reference number) which indicates to the receiver the appropriate shared secret information to use to verify the message. The recipient field contains the name of the recipient of the PKIMessage. This name (in conjunction with recipKID, if supplied) should be usable to verify the protection on the message. The protectionAlg field specifies the algorithm used to protect the message. If no protection bits are supplied (PKIProtection is optional) then this field must be omitted; if protection bits are supplied then this field must be supplied. senderKID and recipKID are usable to indicate which keys have been used to protect the message (recipKID will normally only be required where protection of the message uses DH keys). The transactionID field within the message header is required so that the recipient of a response message can correlate this with a previously issued request. For example, in the case of an RA there may be many requests "outstanding" at a given moment. Farrell, Adams [Page 16] INTERNET-DRAFT December 1996 The senderNonce and recipNonce fields protect the PKIMessage against replay attacks. The messageTime field contains the time at which the sender created the message. This may be useful to allow end entities to correct their local time to be consistent with the time on a central system. The freeText field may be used to send a human-readable message to the recipient. 3.1.2 PKI Message Body PKIBody ::= CHOICE { -- message-specific body elements ir [0] InitReqContent, ip [1] InitRepContent, cr [2] CertReqContent, cp [3] CertRepContent, kur [4] KeyUpdReqContent, kup [5] KeyUpdRepContent, krr [6] KeyRecReqContent, krp [7] KeyRecRepContent, rr [8] RevReqContent, rp [9] RevRepContent, ccr [10] CrossCertReqContent, ccp [11] CrossCertRepContent, ckuann [12] CAKeyUpdAnnContent, cann [13] CertAnnContent, rann [14] RevAnnContent, crlann [15] CRLAnnContent, conf [16] PKIConfirmContent, nested [17] NestedMessageContent, infor [18] PKIInfoReqContent, infop [19] PKIInfoRepContent, error [20] ErrorMsgContent } The specific types are described in section 3.3 below. 3.1.3 PKI Message Protection Some PKI messages will be protected for integrity. (Note that if an asymmetric algorithm is used to protect a message and the relevant public component has been certified already, then the origin of message can also be authenticated. On the other hand, if the public component is uncertified then the message origin cannot be automatically authenticated, but may be authenticated via out-of-band means.) When protection is applied the following structure is used: PKIProtection ::= BIT STRING The input to the calculation of the protectionBits is the DER encoding of the following data structure: ProtectedPart ::= SEQUENCE { Farrell, Adams [Page 17] INTERNET-DRAFT December 1996 header PKIHeader, body PKIBody } Depending on the circumstances the PKIProtection bits may contain a MAC or signature. Only the following cases can occur: - shared secret information In this case the sender and recipient share secret information (established via out-of-band means or from a previous PKI management operation). The protection bits will typically contain a MAC value and the protectionAlg will be the following: PasswordBasedMac ::= OBJECT IDENTIFIER PBMParameter ::= SEQUENCE { salt OCTET STRING, owf AlgorithmIdentifier, -- AlgId for a One-Way Function (SHA-1 recommended) iterationCount INTEGER, -- number of times the OWF is applied mac AlgorithmIdentifier -- the MAC AlgId (e.g., DES-MAC or Triple-DES-MAC [PKCS #11]) } In the above protectionAlg the salt value is appended to the shared secret input. The OWF is then applied iterationCount times, where the salted secret is the input to the first iteration and, for each successive iteration, the input is set to be the output of the previous iteration. The output of the final iteration (called "BASEKEY" for ease of reference, with a size of "H") is what is used to form the symmetric key. If the MAC algorithm requires a K-bit key and K <= H, then the most significant K bits of BASEKEY are used. If K > H, then all of BASEKEY is used for the most significant H bits of the key, OWF("1" || BASEKEY) is used for the next most significant H bits of the key, OWF("2" || BASEKEY) is used for the next most significant H bits of the key, and so on, until all K bits have been derived. [Here "N" is the ASCII byte encoding the number N and "||" represents concatenation.] - DH key pairs Where the sender and receiver possess Diffie-Hellman certificates with compatible DH parameters, then in order to protect the message the end entity must generate a symmetric key based on its private DH key value and the DH public key of the recipient of the PKI message. The protection bits will typically contain a MAC value keyed with this derived symmetric key and the protectionAlg will be the following:. Farrell, Adams [Page 18] INTERNET-DRAFT December 1996 DHBasedMac ::= OBJECT IDENTIFIER DHBMParameter ::= SEQUENCE { owf AlgorithmIdentifier, -- AlgId for a One-Way Function (SHA-1 recommended) mac AlgorithmIdentifier -- the MAC AlgId (e.g., DES-MAC or Triple-DES-MAC [PKCS #11]) } In the above protectionAlg OWF is applied to the result of the Diffie- Hellman computation. The OWF output (called "BASEKEY" for ease of reference, with a size of "H") is what is used to form the symmetric key. If the MAC algorithm requires a K-bit key and K <= H, then the most significant K bits of BASEKEY are used. If K > H, then all of BASEKEY is used for the most significant H bits of the key, OWF("1" || BASEKEY) is used for the next most significant H bits of the key, OWF("2" || BASEKEY) is used for the next most significant H bits of the key, and so on, until all K bits have been derived. [Here "N" is the ASCII byte encoding the number N and "||" represents concatenation.] - signature Where the sender possesses a signature key pair it may simply sign the PKI message. The protection bits will contain a signature value and the protectionAlg will be an AlgorithmIdentifier for a digital signature (e.g., md5WithRSAEncryption or dsaWithSha-1). - multiple protection In cases where an end entity sends a protected PKI message to an RA, the RA may forward that message to a CA, attaching it's own protection. This is accomplished by nesting the entire message sent by the end entity within a new PKI message. The structure used is as follows. NestedMessageContent ::= ANY -- This will be a PKIMessage 3.2 Common Data Structures Before specifying the specific types which may be placed in a PKIBody we define some useful data structures which are used in more than one case. 3.2.1 Requested Certificate Contents Various PKI management messages require that the originator of the message indicate some of the fields which are required to be present in a certificate. The CertTemplate structure allows an end entity or RA to specify as much as they wish about the certificate it requires. ReqCertContent is basically the same as a Certificate but with all fields optional. Note that even if the originator completely specifies the contents of a Farrell, Adams [Page 19] INTERNET-DRAFT December 1996 certificate it requires, a CA is free to modify fields within the certificate actually issued. CertTemplate ::= SEQUENCE { version [0] Version OPTIONAL, -- used to ask for a particular syntax version serial [1] INTEGER OPTIONAL, -- used to ask for a particular serial number signingAlg [2] AlgorithmIdentifier OPTIONAL, -- used to ask the CA to use this alg. for signing the cert subject [3] Name OPTIONAL, validity [4] OptionalValidity OPTIONAL, issuer [5] Name OPTIONAL, publicKey [6] SubjectPublicKeyInfo OPTIONAL, issuerUID [7] UniqueIdentifier OPTIONAL, subjectUID [8] UniqueIdentifier OPTIONAL, extensions [9] Extensions OPTIONAL -- the extensions which the requester would like in the cert. } OptionalValidity ::= SEQUENCE { notBefore [0] UTCTime OPTIONAL, notAfter [1] UTCTime OPTIONAL } 3.2.2 Encrypted Values Where encrypted values (restricted, in this specification, to be either private keys or certificates) are sent in PKI messages the following data structure is used. EncryptedValue ::= SEQUENCE { encValue BIT STRING, -- the encrypted value itself intendedAlg [0] AlgorithmIdentifier OPTIONAL, -- the intended algorithm for which the value will be used symmAlg [1] AlgorithmIdentifier OPTIONAL, -- the symmetric algorithm used to encrypt the value encSymmKey [2] BIT STRING OPTIONAL, -- the (encrypted) symmetric key used to encrypt the value keyAlg [3] AlgorithmIdentifier OPTIONAL -- algorithm used to encrypt the symmetric key } Use of this data structure requires that the creator and intended recipient are respectively able to encrypt and decrypt. Typically, this will mean that the sender and recipient have, or are able to generate, a shared secret key. If the recipient of the PKIMessage already possesses a private key usable for decryption, then the encSymmKey field may contain a session Farrell, Adams [Page 20] INTERNET-DRAFT December 1996 key encrypted using the recipient's public key. 3.2.3 Status codes and Failure Information for PKI messages All response messages will include some status information. The following values are defined. PKIStatus ::= INTEGER { granted (0), -- you got exactly what you asked for grantedWithMods (1), -- you got something like what you asked for; the -- requester is responsible for ascertaining the differences rejection (2), -- you don't get it, more information elsewhere in the message waiting (3), -- the request body part has not yet been processed, -- expect to hear more later revocationWarning (4), -- this message contains a warning that a revocation is -- imminent revocationNotification (5), -- notification that a revocation has occurred keyUpdateWarning (6) -- update already done for the oldCertId specified in -- FullCertTemplate } Responders may use the following syntax to provide more information about failure cases. PKIFailureInfo ::= BIT STRING { -- since we can fail in more than one way! badAlg (0), badMessageCheck (1) -- more TBS } PKIStatusInfo ::= SEQUENCE { status PKIStatus, failInfo PKIFailureInfo OPTIONAL } 3.2.4 Certificate Identification In order to identify particular certificates the following data structure is used. CertId ::= SEQUENCE { issuer GeneralName, serialNumber INTEGER } 3.2.5 "Out-of-band" root CA public key Each root CA must be able to publish its current public key via some Farrell, Adams [Page 21] INTERNET-DRAFT December 1996 "out- of-band" means. While such mechanisms are beyond the scope of this document, we define data structures which can support such mechanisms. There are generally two methods available; either the CA directly publishes its public key and associated attributes, or this information is available via the Directory (or equivalent) and the CA publishes a hash of this value to allow verification of its integrity before use. OOBCert ::= Certificate The fields within this certificate are restricted as follows: - The certificate should be self-signed, i.e. the signature should be verifiable using the subjectPublicKey field. - The subject and issuer fields should be identical. - If the subject field is NULL then both subjectAltNames and issuerAltNames extensions must be present and have exactly the same value. - The values of all other extensions should be suitable for a self- certificate (e.g. key identifiers for subject and issuer should be the same). OOBCertHash ::= SEQUENCE { hashAlg [0] AlgorithmIdentifier OPTIONAL, certId [1] CertId OPTIONAL, hashVal BIT STRING -- hashVal is calculated over DER encoding of the -- subjectPublicKey field of the corresponding cert. } The intention of the hash value here is that anyone who has securely gotten the hash value (via the out-of-band means) can verify a self- signed certificate for that CA. The hash value is only calculated over the subjectPublicKey field in order to allow the CA to change its self- signed certificate (e.g. perhaps to modify some policy constraints). 3.2.6 Archival Options Requesters may indicate that they wish the PKI to archive a private key value using the following structure: PKIArchiveOptions ::= CHOICE { encryptedPrivKey [0] EncryptedValue, -- the actual value of the private key keyGenParameters [1] KeyGenParameters, -- parameters which allow the private key to be re-generated archiveRemGenPrivKey [2] BOOLEAN -- set to TRUE if sender wishes receiver to archive the private -- key of a key pair which the receiver generates in response to -- this request; set to FALSE if no archival is desired. } KeyGenParameters ::= OCTET STRING Farrell, Adams [Page 22] INTERNET-DRAFT December 1996 -- actual syntax is <> -- an alternative to sending the key is to send the information -- about how to re-generate the key (e.g. for many RSA -- implementations one could send the first random number tested -- for primality) <> 3.2.7 Publication Information Requesters may indicate that they wish the PKI to publish a certificate using the structure below. If the dontPublish option is chosen, the requester indicates that the PKI should not publish the certificate (this may indicate that the requester intends to publish the certificate him/herself). If the dontCare method is chosen, the requester indicates that the PKI may publish the certificate using whatever means it chooses. The pubLocation field, if supplied, indicates where the requester would like the certificate to be found (note that the CHOICE within GeneralName includes a URL and an IP address, for example). PKIPublicationInfo ::= SEQUENCE { action INTEGER { dontPublish (0), pleasePublish (1) }, pubInfos SEQUENCE OF SinglePubInfo OPTIONAL -- pubInfos should not be present if action is "dontPublish" -- (if action is "pleasePublish" and pubInfos is omitted, -- "dontCare" is assumed) } SinglePubInfo ::= SEQUENCE { pubMethod INTEGER { dontCare (0), x500 (1), web (2) }, pubLocation GeneralName OPTIONAL } 3.2.8 "Full" Request Template The following structure groups together the fields which may be sent as part of a certification request: FullCertTemplates ::= SEQUENCE OF FullCertTemplate FullCertTemplate ::= SEQUENCE { certReqId INTEGER, -- to match this request with corresponding response -- (note: must be unique over all FullCertReqs in this message) Farrell, Adams [Page 23] INTERNET-DRAFT December 1996 certTemplate CertTemplate, popoSigningKey [0] POPOSigningKey OPTIONAL, archiveOptions [1] PKIArchiveOptions OPTIONAL, publicationInfo [2] PKIPublicationInfo OPTIONAL, oldCertId [3] CertId OPTIONAL -- id. of cert. which is being updated by this one } If the certification request is for a signing key pair (i.e., a request for a verification certificate), then the proof of possession of the private signing key is demonstrated through use of the POPOSigningKey structure. POPOSigningKey ::= SEQUENCE { alg AlgorithmIdentifier, signature BIT STRING -- the signature (using "alg") on the DER-encoded -- POPOSigningKeyInput structure given below } POPOSigningKeyInput ::= SEQUENCE { authInfo CHOICE { sender [0] GeneralName, -- from PKIHeader (used only if an authenticated identity -- has been established for the sender (e.g., a DN from a -- previously-issued and currently-valid certificate) publicKeyMAC [1] BIT STRING -- used if no authenticated GeneralName currently exists for -- the sender; publicKeyMAC contains a password-based MAC -- (using the protectionAlg AlgId from PKIHeader) on the -- DER-encoded value of publicKey } publicKey SubjectPublicKeyInfo -- from CertTemplate } On the other hand, if the certification request is for an encryption key pair (i.e., a request for an encryption certificate), then the proof of possession of the private decryption key may be demonstrated by the inclusion of the private key (encrypted) in the FullCertTemplate (in the PKIArchivalOptions structure). Alternatively (i.e., if the private key is not included), the CA may return not the certificate, but an encrypted certificate (i.e., the certificate encrypted under a randomly- generated symmetric key, and the symmetric key encrypted under the public key for which the certification request is being made). The end entity proves knowledge of the private decryption key to the CA by MACing the PKIConfirm message using a key derived from this symmetric key. [Note that if several FullCertTemplates are included in the PKIMessage, then the CA uses a different symmetric key for each FullCertTemplate and the MAC uses a key derived from the concatenation of all these keys.] The MACing procedure uses the PasswordBasedMac AlgId defined in Section 3.1. Farrell, Adams [Page 24] INTERNET-DRAFT December 1996 3.3 Operation-Specific Data Structures 3.3.1 Initialization Request An Initialization request message (InitReq) contains an InitReqContent data structure which specifies the requested certificate(s). Typically, SubjectPublicKeyInfo, KeyId, and Validity are the template fields which may be supplied for each certificate requested. InitReqContent ::= SEQUENCE { protocolEncKey [0] SubjectPublicKeyInfo OPTIONAL, fullCertTemplates FullCertTemplates } 3.3.2 Initialization Response An Initialization response message (InitRep) contains an InitRepContent data structure which has for each certificate requested a PKIStatusInfo field, a subject certificate, and possibly a private key (normally encrypted with a session key, which is itself encrypted with the protocolEncKey). InitRepContent ::= CertRepContent 3.3.3 Registration/Certification Request A Registration/Certification request message (CertReq) contains a CertReqContent data structure which specifies the requested certificate. CertReqContent ::= FullCertTemplates 3.3.4 Registration/Certification Response A registration response message (CertRep) contains a CertRepContent data structure which has a CA public key, a status value and optionally failure information, a subject certificate, and an encrypted private key. CertRepContent ::= SEQUENCE { caPub [1] Certificate OPTIONAL, response SEQUENCE OF CertResponse } CertResponse ::= SEQUENCE { certReqId INTEGER, -- to match this response with corresponding request status PKIStatusInfo, certifiedKeyPair CertifiedKeyPair OPTIONAL } CertifiedKeyPair ::= SEQUENCE { certificate [0] Certificate OPTIONAL, Farrell, Adams [Page 25] INTERNET-DRAFT December 1996 encryptedCert [1] EncryptedValue OPTIONAL, privateKey [2] EncryptedValue OPTIONAL, publicationInfo [3] PKIPublicationInfo OPTIONAL } Only one of the failInfo (in PKIStatusInfo) and certificate fields should be present in CertRepResponse (depending on the status). For some status values (e.g., waiting) neither of the optional fields will be present. The CertifiedKeyPair structure must contain either a Certificate or an EncryptedCert, and an optional EncryptedPrivateKey (i.e. not both a Certificate and EncryptedCert). Given an EncryptedCert and the relevant decryption key the certificate may be obtained. The purpose of this is to allow a CA to return the value of a certificate, but with the constraint that only the intended recipient can obtain the actual certificate. The benefit of this approach is that a CA may reply with a certificate even in the absence of a proof that the requester is the end entity which can use the relevant private key (note that the proof is not obtained until the PKIConfirm message is received by the CA). Thus the CA will not have to revoke that certificate in the event that something goes wrong. 3.3.5 Key update request content For key update requests the following syntax is used. Typically, SubjectPublicKeyInfo, KeyId, and Validity are the template fields which may be supplied for each key to be updated. KeyUpdReqContent ::= SEQUENCE { protocolEncKey [0] SubjectPublicKeyInfo OPTIONAL, fullCertTemplates [1] FullCertTemplates OPTIONAL } 3.3.6 Key Update response content For key update responses the syntax used is identical to the initialization response. KeyUpdRepContent ::= InitRepContent 3.3.7 Key Recovery Request content For key recovery requests the syntax used is identical to the initialization request InitReqContent. Typically, SubjectPublicKeyInfo and KeyId are the template fields which may be used to supply a signature public key for which a certificate is required. KeyRecReqContent ::= InitReqContent 3.3.8 Key recovery response content For key recovery responses the following syntax is used. For some Farrell, Adams [Page 26] INTERNET-DRAFT December 1996 status values (e.g., waiting) none of the optional fields will be present. KeyRecRepContent ::= SEQUENCE { status PKIStatusInfo, newSigCert [0] Certificate OPTIONAL, caCerts [1] SEQUENCE OF Certificate OPTIONAL, keyPairHist [2] SEQUENCE OF CertifiedKeyPair OPTIONAL } 3.3.9 Revocation Request Content When requesting revocation of a certificate (or several certificates) the following data structure is used. The name of the requester is present in the PKIHeader structure. RevReqContent ::= SEQUENCE OF RevDetails RevDetails ::= SEQUENCE { certDetails CertTemplate, -- allows requester to specify as much as they can about -- the cert. for which revocation is requested -- (e.g. for cases in which serialNumber is not available) revocationReason ReasonFlags, -- from the DAM, so that CA knows which Dist. point to use badSinceDate GeneralizedTime OPTIONAL, -- indicates best knowledge of sender crlEntryDetails Extensions -- requested crlEntryExtensions } 3.3.10 Revocation Response Content The response to the above message. If produced, this is sent to the requester of the revocation. (A separate revocation announcement message may be sent to the subject of the certificate for which revocation was requested.) RevRepContent ::= SEQUENCE { status PKIStatusInfo, revCerts [0] SEQUENCE OF CertId OPTIONAL, -- identifies the certs for which revocation was requested crls [1] SEQUENCE OF CertificateList OPTIONAL -- the resulting CRLs (there may be more than one) } 3.3.11 Cross certification request content Cross certification requests use the same syntax as for normal certification requests with the restriction that the key should have been generated by the requesting CA and should not be sent to the responding CA. CrossCertReqContent ::= CertReqContent Farrell, Adams [Page 27] INTERNET-DRAFT December 1996 3.3.12 Cross certification response content Cross certification responses use the same syntax as for normal certification responses with the restriction that no encrypted private key can be sent. CrossCertRepContent ::= CertRepContent 3.3.13 CA Key Update Announcement content When a CA updates its own key pair the following data structure may be used to announce this event. CAKeyUpdAnnContent ::= SEQUENCE { oldWithNew Certificate, -- old pub signed with new priv newWithOld Certificate, -- new pub signed with old priv newWithNew Certificate -- new pub signed with new priv } 3.3.14 Certificate Announcement This data structure may be used to announce the existence of certificates. Note that this structure (and the CertAnn message itself) is intended to be used for those cases (if any) where there is no pre-existing method for publication of certificates; it is not intended to be used where, for example, X.500 is the method for publication of certificates. CertAnnContent ::= Certificate 3.3.15 Revocation Announcement When a CA has revoked, or is about to revoke, a particular certificate it may issue an announcement of this (possibly upcoming) event. RevAnnContent ::= SEQUENCE { status PKIStatus, certId CertId, willBeRevokedAt GeneralizedTime, badSinceDate GeneralizedTime, crlDetails Extensions OPTIONAL -- extra CRL details(e.g., crl number, reason, location, etc.) } A CA may use such an announcement to warn (or notify) a subject that its certificate is about to be (or has been) revoked. This would typically be used where the request for revocation did not come from the subject concerned. The willBeRevokedAt field contains the time at which a new entry will be added to the relevant CRLs. 3.3.16 CRL Announcement 3.3.17 Farrell, Adams [Page 28] INTERNET-DRAFT December 1996 When a CA issues a new CRL (or set of CRLs) the following data structure may be used to announce this event. CRLAnnContent ::= SEQUENCE OF CertificateList 3.3.18 PKI Confirmation content This data structure is used in three-way protocols as the final PKIMessage. Its content is the same in all cases - actually there is no content since the PKIHeader carries all the required information. PKIConfirmContent ::= NULL 3.3.19 PKI Information Request content PKIInfoReqContent ::= BIT STRING { caProtEncCert (0), signKeyPairTypes (1), enckeyPairTypes (2), preferredSymmAlg (3), caKeyUpdateInfo (4), currentCRL (5) } 3.3.20 PKI Information Response content PKIInfoRepContent ::= SEQUENCE { caProtEncCert [0] Certificate OPTIONAL, signKeyPairTypes [1] SEQUENCE OF AlgorithmIdentifier OPTIONAL, encKeypairTypes [2] SEQUENCE OF AlgorithmIdentifier OPTIONAL, preferredSymmAlg [3] AlgorithmIdentifier OPTIONAL, caKeyUpdateInfo [4] CAKeyUpdAnnContent OPTIONAL, currentCRL [5] CertificateList OPTIONAL } 3.3.21 Error Message content ErrorMsgContent ::= SEQUENCE { pKIStatusInfo PKIStatusInfo, errorCode INTEGER OPTIONAL, -- implementation-specific error codes errorDetails CHOICE { IA5String, BMPString } OPTIONAL -- implementation-specific error details } 4. PKI Management functions The PKI management functions outlined in section 1 above are described in this section. This section is split into two, the first part dealing with functions which are "mandatory" in the sense that all end-entity and CA/RA implementations must be able to provide functionality described via one of the transport mechanisms defined in section 5. This part is effectively the profile of the PKI management functionality which must be supported. Farrell, Adams [Page 29] INTERNET-DRAFT December 1996 The second part defines "additional" functions. Note that not all PKI management functions result in the creation of a PKI message. 4.1 Mandatory Functions 4.1.1 Root CA initialisation A newly created root CA must produce a "self-certificate" which is a Certificate structure with the profile defined for the "newWithNew" certificate issued following a root CA key update. In order to make the CA's self certificate useful to end entities which do not acquire this information via "out-of-band" means, the CA must also produce a fingerprint for its public key. End entities which acquire this value securely via some "out-of-band" means can then verify the CA's self-certificate and hence the other attributes contained therein. The data structure used to carry the fingerprint is the OOBCertHash. The root CA must also produce an initial revocation list. 4.1.2 Root CA key update 4.1.3 Subordinate CA initialisation From the perspective of PKI management protocols the initialisation of a subordinate CA is the same as the initialisation of an end-entity. The only difference is that the subordinate CA must also produce an initial revocation list. 4.1.4 CRL production Before issuing any certificates a newly established CA (which issues CRLs) must produce "empty" versions of each CRL which is to be periodically produced. 4.1.5 PKI information request The above operations produce various data structures which are used in PKI management protocols. When a PKI entity wishes to acquire information about the current status of a CA it may send that CA a PKIInfoReq PKIMessage. The response will be a PKIInfoRep message. The CA should respond to the request with a response providing all of the information requested by the requester. If some of the information cannot be provided then an error message should be returned. The PKIInfoReq and PKIInfoRep messages are protected using a MAC based on shared secret information (i.e., PasswordBasedMAC) or any other authenticated means (if the end entity has an existing certificate). 4.1.6 Cross certification The initiating CA is the CA which will become the subject of the cross- certificate, the responding CA will become the issuer of the cross- Farrell, Adams [Page 30] INTERNET-DRAFT December 1996 certificate. The initiating CA must be "up and running" before initiating the cross- certification operation. As with registration/certification there are a few possibilities here. 4.1.6.1 One-way request-response scheme: The cross-certification scheme is essentially a one way operation; that is, when successful, this operation results in the creation of one new cross-certificate. If the requirement is that cross- certificates be created in "both directions" then each CA in turn must initiate a cross- certification operation (or use another scheme). This scheme is suitable where the two CAs in question can already verify each other's signatures (they have some common points of trust) or where there is an out-of-band verification of the origin of the certification request. The followings steps occur: 1.The initiating CA gathers the information required for the cross certification request; 2.The initiating CA creates the cross-certification request message (CrossCertReq); 3.The CrossCertReq message is transported to the responding CA; 4.The responding CA processes the CrossCertReq -- this results in the creation of a cross-certification response (CrossCertRep) message; 5.The CrossCertRep message is transported to the initiating CA; 6.The initiating CA processes the CrossCertRep (depending on its content some looping may be required; that is, the initiating CA may have to await further responses or generate a new CrossCertReq for the responding CA); 7.The initiating CA creates a PKIConfirm message and transports it to the responding CA. Notes: 1.The CrossCertReq should contain a "complete" certification request, that is, all fields (including e.g. a BasicConstraints extension) should be specified by the initiating CA. 2.The CrossCertRep message should contain the verification certificate of the responding CA - the initiating CA should then verify this via the "out-of-band" mechanism. 4.1.7 End entity initialisation As with CAs, end entity's must be initialised. Initialisation of end entities requires two steps: - acquisition of PKI information - out-of-band verification of root-CA public key 4.1.7.1 Acquisition of PKI information The information required is: Farrell, Adams [Page 31] INTERNET-DRAFT December 1996 - the current root-CA public key - (if the certifying CA is not a root-CA) the certification path from the root CA to the certifying CA together with appropriate revocation lists - the algorithms and algorithm parameters which the certifying CA supports for each relevant usage Additional information could be required (e.g. supported extensions or CA policy information) in order to produce a certification request which will be successful. However, for simplicity we do not mandate that the end entity acquires this information via the PKI messages. The end result is simply that some certification requests may fail (e.g., if the end entity wants to generate its own encryption key but the CA doesn't allow that). The required information is acquired as follows: - the end entity sends a pKIInfoReq to the certifying CA requesting (with the xxxxxx bits set) the information it requires; - the certifying CA responds with a pKIInfoRep message which contains the requested information. 4.1.8 Certificate Update When a certificate is due to expire the relevant end entity may request that the CA update the certificate - that is, that the CA issue a new certificate which differs from the previous one only in terms of PKI attributes (serialNumber, validity, some extensions) and is otherwise identical. Two options must be catered for here, where the end entity initiates this operation, and where the CA initiates the operation and then creates a message informing the end entity of the existence of the new certificate. 4.2 Additional Functions 4.2.1 Cross certification 4.2.1.1 Two-way request-response scheme: 4.2.1.1.1 Overview of Exchange This cross certification exchange allows two CAs to simultaneously certify each other. This means that each CA will create a certificate that contains the CA verification key of the other CA. Cross certification is initiated at one CA known as the responder. The CA administrator for the responder identifies the CA it wants to cross certify and the responder CA equipment generates an authorization code. The responder CA administrator passes this authorization code by out-of- band means to the requester CA administrator. The requester CA administrator enters the authorization code at the requester CA in order to initiate the on-line exchange. Farrell, Adams [Page 32] INTERNET-DRAFT December 1996 The authorization code is used for authentication and integrity purposes. This is done by generating a symmetric key based on the authorization code and using the symmetric key for generating Message Authentication Codes (MACs) on all messages exchanged. Serial numbers and protocol version are used in the same manner as in the above CA-client exchanges. 4.2.1.1.2 Detailed Description The requester CA initiates the exchange by generating a random number (requester random number). The requester CA then sends the responder CA the message CrossReq. The fields in this message are protected from modification with a MAC based on the authorization code. Upon receipt of the CrossReq message, the responder CA checks the protocol version, saves the requester random number, generates its own random number (responder random number) and validates the MAC. It then generates and archives a new requester certificate which contains the requester CA public key and is signed with the responder CA signature private key. The responder CA responds with the message CrossRep. The fields in this message are protected from modification with a MAC based on the authorization code. Upon receipt of the CrossRep message, the requester CA checks that its own system time is close to the responder CA system time, checks the received random numbers and validates the MAC. It then generates and archives a new responder certificate which contains the responder CA public key and is signed by the requester CA signature private key. The requester CA responds with the message PKIConfirm. The fields in this message are protected from modification with a MAC based on the authorization code. Upon receipt of the PKIConfirm message, the responder CA checks the random numbers, archives the responder certificate, and validates the MAC. It writes both the request and responder certificates to the Directory. It then responds with its own PKIConfirm message. The fields in this message are protected from modification with a MAC based on the authorization code. Upon receipt of the PKIConfirm message, the requester CA checks the random numbers and validates the MAC. The requester CA writes both the requester and responder certificates to the Directory. 4.2.2 End entity initialisation As with CAs, end entities must be initialised. Initialisation of end entities requires two steps: - acquisition of PKI information - out-of-band verification of root-CA public key 4.2.2.1 Acquisition of PKI information See previous section. Farrell, Adams [Page 33] INTERNET-DRAFT December 1996 4.2.2.2 Import of CA key fingerprint An end entity must possess the public key of it's root CA. One method to achieve this is to provide the end entity with the CA's public key fingerprint via some secure "out-of-band" means. The end entity can then securely use the CA's self-certificate. The data structure used is the OOBcertHash 5. Transports The transport protocols specified below allow end entities, RAs and CAs to pass PKI messages between them. There should be no requirement for specific security mechanisms to be applied at this level as the PKI messages should be suitably protected. Caution should be taken that no "password" encrypted value is sent across a network using these protocols. If values are to be encrypted based on passwords then they should be transported using off-line means (e.g. files). 5.1 File based protocol A file containing a PKI message should contain only the DER encoding of one PKI message, i.e. there should be no extraneous header or trailer information in the file. Such files can be used to transport PKI messages using e.g. FTP. 5.2 Socket based Management Protocol The following simple socket based protocol is to be used for transport of PKI messages. This protocol is suitable for cases where an end entity (or an RA) initiates a transaction and can poll to pick up the results. If a transaction is initiated by a PKI entity (RA or CA) then an end entity must either supply a listener process or be supplied with a polling reference (see below) in order to allow it to pick up the PKI message from the PKI management component. The protocol basically assumes a listener process (on an RA or CA) which can accept PKI messages on a well defined port (port number TBS). Typically an initiator binds to this port and submits the initial PKI message for a given transaction ID. The responder replies with a PKI message and/or with a reference number to be used later when polling for the actual PKI message response. If a number of PKI response messages are to be produced for a given request (say if some part of the request is handled more quickly than another) then a new polling reference is also returned. When the final PKI response message has been picked up by the initiator then no new polling reference is supplied. The initiator of a transaction sends a "socket PKI message" to the recipient. The recipient responds with a similar message. Farrell, Adams [Page 34] INTERNET-DRAFT December 1996 A "socket PKI message" consists of: length (32-bits), flag (8-bits), value (defined below) The length field contains the number of octets of the remainder of the message (i.e. number of octets of "value" plus one). Message name flag value comment msgReq `00'H DER-encoded PKI message PKI message from initiator pollRep `01'H polling reference (32-bits) poll response where no PKI message response ready; use polling reference value for later polling pollReq `02'H polling reference (32 bits) request for a PKI message response to initial message negPollRep `03'H `00'H no further polling responses (i.e., transaction complete) partialMsgRep `04'H next polling reference partial response to initial (32-bits), message plus new polling DER encoded PKI message reference to use to get next part of response finalMsgRep `05'H DER encoded PKI message final (and possibly sole) response to initial message errorMsgRep `06'H human readable error produced when an error is message detected (e.g., a polling reference is received which doesn't exist or is finished with) Where a PKIConfirm message is to be transported (always from the initiator to the responder) then a msgReq message is sent and a negPollRep is returned. The sequence of messages which can occur is then: a) end entity sends msgReq and receives one of pollRep, negPollRep, partialMsgRep or finalMsgRep in response. b) end entity sends pollReq message and receives one of negPollRep, partialMsgRep, finalMsgRep or ErrorMsgRep in response. 5.3 Management Protocol via E-mail << To be supplied. This subsection will specify a means for conveying ASN.1-encoded messages for the protocol exchanges described in Section 4 via Internet mail. >> Farrell, Adams [Page 35] INTERNET-DRAFT December 1996 5.4 Management Protocol via HTTP << To be supplied. This subsection will specify a means for conveying ASN.1-encoded messages for the protocol exchanges described in Section 4 over WWW browser-server links, employing HTTP or related WWW protocols. >> 6. SAMPLES <> SECURITY CONSIDERATIONS This entire memo is about security mechanisms. One cryptographic consideration is worth explicitly spelling out. In the protocols specified above, when an end entity is required to prove possession of a decryption key, it is effectively challenged to decrypt something (its own certificate). This scheme (and many others!) could be vulnerable to an attack if the possessor of the decryption key in question could be fooled into decrypting an arbitrary challenge and returning the cleartext to an attacker. Although in this specification a number of other failures in security are required in order for this attack to succeed, it is conceivable that some future services (e.g., notary, trusted time) could potentially be vulnerable to such attacks. For this reason we re-iterate the general rule that implementations should be very careful about decrypting arbitrary "ciphertext" and revealing recovered "plaintext" since such a practice can lead to serious security vulnerabilities. Authors' Addresses Stephen Farrell Software and Systems Engineering Ltd. Fitzwilliam Court Leeson Close Dublin 2 IRELAND stephen.farrell@sse.ie Carlisle Adams Nortel Secure Networks PO Box 3511, Station C Ottawa, Ontario Canada K1Y 4H7 cadams@entrust.com APPENDIX A: Reasons for the presence of RAs The reasons which justify the presence of an RA can be split into those which are due to technical factors and those which are organizational in nature. Technical reasons include the following. -If hardware tokens are in use, then not all end entities will have the equipment needed to initialize these; the RA equipment can include the necessary functionality (this may also be a matter of policy). -Some end entities may not have the capability to publish certificates; again, the RA may be suitably placed for this. -The RA will be able to issue signed revocation requests on behalf of end entities associated with it, whereas the end entity may not be able to do this (if the key pair is completely lost). Farrell, Adams [Page 36] INTERNET-DRAFT December 1996 Some of the organisational reasons which argue for the presence of an RA are the following. -It may be more cost effective to concentrate functionality in the RA equipment than to supply functionality to all end entities (especially if special token initialization equipment is to be used). -Establishing RAs within an organization can reduce the number of CAs required, which is sometimes desirable. -RAs may be better placed to identify people with their "electronic" names, especially if the CA is physically remote from the end entity. -For many applications there will already be in place some administrative structure so that candidates for the role of RA are easy to find (which may not be true of the CA). Appendix B. PKI management message profiles. This appendix contains detailed profiles for those PKIMessages which must be supported by conforming implementations. Profiles for the PKIMessages used in the following PKI management operations are provided: - root CA key update - information request/reponse - cross-certification (1-way) - initial registration and certification - centralised scheme - basic authenticated scheme <> - certificate update - end entity initiated - PKI initiated - key update - revocation request - certificate publcation - CRL publication 1. General Rules for interpretation of these profiles. 1. Where fields are not mentioned in individual profiles then they should be absent (if OPTIONAL or DEFAULT) from the relevant message. For example, pvno is never mentioned since it is always fixed for this version of the specification. 2. Where structures occur in more than one message, they are separately profiled as appropriate. 3. The algorithmIdentifiers from PKIMessage structures are profiled separately. 4. A "special" X.500 DN is called the "NULL-DN"; this means a DN containing a zero- 5. Farrell, Adams [Page 37] INTERNET-DRAFT December 1996 1. length SEQUENCE OF rdns (it's DER encoding is then `3000'H). 2. Where a GeneralName is required for a field but no suitable value is available (e.g. an end-entity produces a request before knowing its name) then the GeneralName is to be an X.500 NULL-DN (i.e. the Name field of the CHOICE is to contain a NULL-DN). This special value can be called a "NULL-GeneralName". 3. Where a profile omits to specify the value for a GeneralName then the NULL-GeneralName value is to be present in the relevant PKIMessage field. This occurs with the sender field of the PKIHeader for some messages. 4. Where any ambiguity arises due to naming of fields, the profile names these using a "dot" notation (e.g., "certTemplate.subject" means the subject field within a field called certTemplate). 5. Where a "SEQUENCE OF types" is part of a message, a zero-based array notation is used to describe fields within the SEQUENCE OF (e.g., FullCertTemplates[0].certTemplate.subject refers to a subfield of the first FullCertTemplate contained in a request message). 6. All PKI message exchanges (other than the centralised initial registration/certification scheme) require a PKIConfirm message to be sent by the initiating entity. This message is not included in many of the profiles given below since its body is NULL and its header contents are clear from the context. Any authenticated means can be used for the protectionAlg (e.g., password-based MAC, if shared secret information is known, or signature). <> Appendix C: "Compilable" ASN.1 Module PKIMessage ::= SEQUENCE { header PKIHeader, body PKIBody, protection [0] PKIProtection OPTIONAL, extraCerts [1] SEQUENCE OF Certificate OPTIONAL Farrell, Adams [Page 38] INTERNET-DRAFT December 1996 } PKIHeader ::= SEQUENCE { pvno INTEGER { ietf-version1 (0) }, sender GeneralName, -- identifies the sender recipient GeneralName, -- identifies the intended recipient messageTime [0] GeneralizedTime OPTIONAL, -- time of production of this message (used when sender -- believes that the transport will be "suitable"; i.e., -- that the time will still be meaningful upon receipt) protectionAlg [1] AlgorithmIdentifier OPTIONAL, -- algorithm used for calculation of protection bits senderKID [2] KeyIdentifier OPTIONAL, recipKID [3] KeyIdentifier OPTIONAL, -- to identify specific keys used for protection transactionID [4] OCTET STRING OPTIONAL, -- identifies the transaction, i.e. this will be the same in -- corresponding request, response and confirmation messages senderNonce [5] OCTET STRING OPTIONAL, recipNonce [6] OCTET STRING OPTIONAL, -- nonces used to provide replay protection, senderNonce -- is inserted by the creator of this message; recipNonce -- is a nonce previously inserted in a related message by -- the intended recipient of this message freeText [7] PKIFreeText OPTIONAL -- this may be used to indicate context-specific -- instructions (this field is intended for human -- consumption) } PKIFreeText ::= CHOICE { iA5String [0] IA5String, bMPString [1] BMPString } PKIBody ::= CHOICE { -- message-specific body elements ir [0] InitReqContent, ip [1] InitRepContent, cr [2] CertReqContent, cp [3] CertRepContent, kur [4] KeyUpdReqContent, kup [5] KeyUpdRepContent, krr [6] KeyRecReqContent, krp [7] KeyRecRepContent, rr [8] RevReqContent, rp [9] RevRepContent, ccr [10] CrossCertReqContent, ccp [11] CrossCertRepContent, ckuann [12] CAKeyUpdAnnContent, cann [13] CertAnnContent, Farrell, Adams [Page 39] INTERNET-DRAFT December 1996 rann [14] RevAnnContent, crlann [15] CRLAnnContent, conf [16] PKIConfirmContent, nested [17] NestedMessageContent, infor [18] PKIInfoReqContent, infop [19] PKIInfoRepContent, error [20] ErrorMsgContent } PKIProtection ::= BIT STRING ProtectedPart ::= SEQUENCE { header PKIHeader, body PKIBody } PasswordBasedMac ::= OBJECT IDENTIFIER PBMParameter ::= SEQUENCE { salt OCTET STRING, owf AlgorithmIdentifier, -- AlgId for a One-Way Function (SHA-1 recommended) iterationCount INTEGER, -- number of times the OWF is applied mac AlgorithmIdentifier -- the MAC AlgId (e.g., DES-MAC or Triple-DES-MAC [PKCS #11]) } DHBasedMac ::= OBJECT IDENTIFIER DHBMParameter ::= SEQUENCE { owf AlgorithmIdentifier, -- AlgId for a One-Way Function (SHA-1 recommended) mac AlgorithmIdentifier -- the MAC AlgId (e.g., DES-MAC or Triple-DES-MAC [PKCS #11]) } NestedMessageContent ::= ANY -- This will be a PKIMessage CertTemplate ::= SEQUENCE { version [0] Version OPTIONAL, -- used to ask for a particular syntax version serial [1] INTEGER OPTIONAL, -- used to ask for a particular serial number signingAlg [2] AlgorithmIdentifier OPTIONAL, -- used to ask the CA to use this alg. for signing the cert subject [3] Name OPTIONAL, validity [4] OptionalValidity OPTIONAL, issuer [5] Name OPTIONAL, publicKey [6] SubjectPublicKeyInfo OPTIONAL, issuerUID [7] UniqueIdentifier OPTIONAL, Farrell, Adams [Page 40] INTERNET-DRAFT December 1996 subjectUID [8] UniqueIdentifier OPTIONAL, extensions [9] Extensions OPTIONAL -- the extensions which the requester would like in the cert. } OptionalValidity ::= SEQUENCE { notBefore [0] UTCTime OPTIONAL, notAfter [1] UTCTime OPTIONAL } EncryptedValue ::= SEQUENCE { encValue BIT STRING, -- the encrypted value itself intendedAlg [0] AlgorithmIdentifier OPTIONAL, -- the intended algorithm for which the value will be used symmAlg [1] AlgorithmIdentifier OPTIONAL, -- the symmetric algorithm used to encrypt the value encSymmKey [2] BIT STRING OPTIONAL, -- the (encrypted) symmetric key used to encrypt the value keyAlg [3] AlgorithmIdentifier OPTIONAL -- algorithm used to encrypt the symmetric key } PKIStatus ::= INTEGER { granted (0), -- you got exactly what you asked for grantedWithMods (1), -- you got something like what you asked for; the -- requester is responsible for ascertaining the differences rejection (2), -- you don't get it, more information elsewhere in the message waiting (3), -- the request body part has not yet been processed, -- expect to hear more later revocationWarning (4), -- this message contains a warning that a revocation is -- imminent revocationNotification (5), -- notification that a revocation has occurred keyUpdateWarning (6) -- update already done for the oldCertId specified in -- FullCertTemplate } PKIFailureInfo ::= BIT STRING { -- since we can fail in more than one way! badAlg (0), badMessageCheck (1) -- more TBS } PKIStatusInfo ::= SEQUENCE { Farrell, Adams [Page 41] INTERNET-DRAFT December 1996 status PKIStatus, failInfo PKIFailureInfo OPTIONAL } CertId ::= SEQUENCE { issuer GeneralName, serialNumber INTEGER } OOBCert ::= Certificate OOBCertHash ::= SEQUENCE { hashAlg [0] AlgorithmIdentifier OPTIONAL, certId [1] CertId OPTIONAL, hashVal BIT STRING -- hashVal is calculated over DER encoding of the -- subjectPublicKey field of the corresponding cert. } PKIArchiveOptions ::= CHOICE { encryptedPrivKey [0] EncryptedValue, -- the actual value of the private key keyGenParameters [1] KeyGenParameters, -- parameters which allow the private key to be re-generated archiveRemGenPrivKey [2] BOOLEAN -- set to TRUE if sender wishes receiver to archive the private -- key of a key pair which the receiver generates in response to -- this request; set to FALSE if no archival is desired. } KeyGenParameters ::= OCTET STRING -- actual syntax is <> -- an alternative to sending the key is to send the information -- about how to re-generate the key (e.g. for many RSA -- implementations one could send the first random number tested -- for primality) PKIPublicationInfo ::= SEQUENCE { action INTEGER { dontPublish (0), pleasePublish (1) }, pubInfos SEQUENCE OF SinglePubInfo OPTIONAL -- pubInfos should not be present if action is "dontPublish" -- (if action is "pleasePublish" and pubInfos is omitted, -- "dontCare" is assumed) } SinglePubInfo ::= SEQUENCE { pubMethod INTEGER { dontCare (0), x500 (1), Farrell, Adams [Page 42] INTERNET-DRAFT December 1996 web (2) }, pubLocation GeneralName OPTIONAL } FullCertTemplates ::= SEQUENCE OF FullCertTemplate FullCertTemplate ::= SEQUENCE { certReqId INTEGER, -- to match this request with corresponding response -- (note: must be unique over all FullCertReqs in this message) certTemplate CertTemplate, popoSigningKey [0] POPOSigningKey OPTIONAL, archiveOptions [1] PKIArchiveOptions OPTIONAL, publicationInfo [2] PKIPublicationInfo OPTIONAL, oldCertId [3] CertId OPTIONAL -- id. of cert. which is being updated by this one } POPOSigningKey ::= SEQUENCE { alg AlgorithmIdentifier, signature BIT STRING -- the signature (using "alg") on the DER-encoded -- POPOSigningKeyInput structure given below } POPOSigningKeyInput ::= SEQUENCE { authInfo CHOICE { sender [0] GeneralName, -- from PKIHeader (used only if an authenticated identity -- has been established for the sender (e.g., a DN from a -- previously-issued and currently-valid certificate) publicKeyMAC [1] BIT STRING -- used if no authenticated GeneralName currently exists for -- the sender; publicKeyMAC contains a password-based MAC -- (using the protectionAlg AlgId from PKIHeader) on the -- DER-encoded value of publicKey }, publicKey SubjectPublicKeyInfo -- from CertTemplate } InitReqContent ::= SEQUENCE { protocolEncKey [0] SubjectPublicKeyInfo OPTIONAL, fullCertTemplates FullCertTemplates } InitRepContent ::= CertRepContent CertReqContent ::= FullCertTemplates CertRepContent ::= SEQUENCE { caPub [1] Certificate OPTIONAL, Farrell, Adams [Page 43] INTERNET-DRAFT December 1996 response SEQUENCE OF CertResponse } CertResponse ::= SEQUENCE { certReqId INTEGER, -- to match this response with corresponding request status PKIStatusInfo, certifiedKeyPair CertifiedKeyPair OPTIONAL } CertifiedKeyPair ::= SEQUENCE { certificate [0] Certificate OPTIONAL, encryptedCert [1] EncryptedValue OPTIONAL, privateKey [2] EncryptedValue OPTIONAL, publicationInfo [3] PKIPublicationInfo OPTIONAL } KeyUpdReqContent ::= SEQUENCE { protocolEncKey [0] SubjectPublicKeyInfo OPTIONAL, fullCertTemplates [1] FullCertTemplates OPTIONAL } KeyUpdRepContent ::= InitRepContent KeyRecReqContent ::= InitReqContent KeyRecRepContent ::= SEQUENCE { status PKIStatusInfo, newSigCert [0] Certificate OPTIONAL, caCerts [1] SEQUENCE OF Certificate OPTIONAL, keyPairHist [2] SEQUENCE OF CertifiedKeyPair OPTIONAL } RevReqContent ::= SEQUENCE OF RevDetails RevDetails ::= SEQUENCE { certDetails CertTemplate, -- allows requester to specify as much as they can about -- the cert. for which revocation is requested -- (e.g. for cases in which serialNumber is not available) revocationReason ReasonFlags, -- from the DAM, so that CA knows which Dist. point to use badSinceDate GeneralizedTime OPTIONAL, -- indicates best knowledge of sender crlEntryDetails Extensions -- requested crlEntryExtensions } RevRepContent ::= SEQUENCE { status PKIStatusInfo, revCerts [0] SEQUENCE OF CertId OPTIONAL, -- identifies the certs for which revocation was requested Farrell, Adams [Page 44] INTERNET-DRAFT December 1996 crls [1] SEQUENCE OF CertificateList OPTIONAL -- the resulting CRLs (there may be more than one) } CrossCertReqContent ::= CertReqContent CrossCertRepContent ::= CertRepContent CAKeyUpdAnnContent ::= SEQUENCE { oldWithNew Certificate, -- old pub signed with new priv newWithOld Certificate, -- new pub signed with old priv newWithNew Certificate -- new pub signed with new priv } CertAnnContent ::= Certificate RevAnnContent ::= SEQUENCE { status PKIStatus, certId CertId, willBeRevokedAt GeneralizedTime, badSinceDate GeneralizedTime, crlDetails Extensions OPTIONAL -- extra CRL details(e.g., crl number, reason, location, etc.) } CRLAnnContent ::= SEQUENCE OF CertificateList PKIConfirmContent ::= NULL PKIInfoReqContent ::= BIT STRING { caProtEncCert (0), signKeyPairTypes (1), enckeyPairTypes (2), preferredSymmAlg (3), caKeyUpdateInfo (4), currentCRL (5) } PKIInfoRepContent ::= SEQUENCE { caProtEncCert [0] Certificate OPTIONAL, signKeyPairTypes [1] SEQUENCE OF AlgorithmIdentifier OPTIONAL, encKeypairTypes [2] SEQUENCE OF AlgorithmIdentifier OPTIONAL, preferredSymmAlg [3] AlgorithmIdentifier OPTIONAL, caKeyUpdateInfo [4] CAKeyUpdAnnContent OPTIONAL, currentCRL [5] CertificateList OPTIONAL } ErrorMsgContent ::= SEQUENCE { pKIStatusInfo PKIStatusInfo, errorCode INTEGER OPTIONAL, -- implementation-specific error codes errorDetails CHOICE { IA5String, BMPString } OPTIONAL Farrell, Adams [Page 45] INTERNET-DRAFT December 1996 -- implementation-specific error details }