Network Working Group J. Schaad Internet-Draft Soaring Hawk Consulting Intended status: Informational April 24, 2012 Expires: October 26, 2012 S/MIME Capabilities for Public Key Definitions draft-ietf-pkix-pubkey-caps-05 Abstract This document defines a set of S/MIME Capability types for ASN.1 encoding for the current set of public keys define in the PKIX working group. This facilitates the ability for a requester to specify information on the public keys and signature algorithms to be used in responses. An example of where this is used is with the OCSP Agility draft. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six 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." This Internet-Draft will expire on October 26, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as Schaad Expires October 26, 2012 [Page 1] Internet-Draft PubKey Caps April 2012 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. ASN.1 Notation . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Terminology . . . . . . . . . . . . . . . . . 4 2. RSA Public Keys . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Generic RSA Public Keys . . . . . . . . . . . . . . . . . 5 2.2. RSASSA-PSS Signature Public Keys . . . . . . . . . . . . . 6 2.3. RSA ES-OAEP Key Transport Public Keys . . . . . . . . . . 6 3. Diffie-Hellman Keys . . . . . . . . . . . . . . . . . . . . . 8 3.1. DSA Signature Public Key . . . . . . . . . . . . . . . . . 8 3.2. DH Key Agreement Keys . . . . . . . . . . . . . . . . . . 9 4. Elliptical Curve Keys . . . . . . . . . . . . . . . . . . . . 10 4.1. Generic Elliptical Curve Keys . . . . . . . . . . . . . . 10 4.2. Elliptical Curve DH Keys . . . . . . . . . . . . . . . . . 11 4.3. Elliptical Curve MQV Keys . . . . . . . . . . . . . . . . 11 5. RSASSA-PSS Signature Algorithm Capability . . . . . . . . . . 12 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8.1. Normative References . . . . . . . . . . . . . . . . . . . 17 8.2. Informative References . . . . . . . . . . . . . . . . . . 17 Appendix A. 2008 ASN.1 Module . . . . . . . . . . . . . . . . . . 18 Appendix B. 1988 ASN.1 Module . . . . . . . . . . . . . . . . . . 21 Appendix C. Future Work . . . . . . . . . . . . . . . . . . . . . 23 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 24 Schaad Expires October 26, 2012 [Page 2] Internet-Draft PubKey Caps April 2012 1. Introduction In the process of dealing with the OCSP agility issues in [RFC6277] it was noted that we really wanted to describe information to be used in selecting a public key, but we did not currently have any way of doing so at the current time. This document fills that hole by defining a set of S/MIME Capability types for a small set of public key representations. S/MIME Capabilities where originally defined in [SMIMEv3-MSG] as a way for the sender of an S/MIME message to tell the recipient of the message the set of encryption algorithms that were supported by the sender's system. In the beginning, the focus was primarily on communicating the set of encryption algorithms that were supported. Over time it was expanded to allow for an S/MIME client to say that it supported the compression data type and binary contents. As originally defined it was targeted toward supporting items with a small number of possible parameters. For the RC2 encryption algorithm only two values from the entire range of values were ever used. The object of restricting the set of values was so that a client could do a simple binary comparison without having to decode the S/MIME capability. This was especially easy since most just consisted of the object identifier for the algorithm. Many people are under the impression that only a single data structure can be assigned to an object identifer, this is not the case. As an example the OID rsaEncryption is used in multiple locations for different data. It represents a public key, a key transport algoritm (in S/MIME), and was originally used in the PKCS#7 specfication as a signature value identifier (this has since been changed by the S/MIME specifications). One of the implications is that when mapping an object identifier to a data type structure, the location in the ASN.1 structure need to be taken into consideration as well. 1.1. ASN.1 Notation The main body of the text is written using snippets of ASN.1 that are extracted from the ASN.1 2008 module in Appendix A. ASN.1 2008 is used in the document because it directly represents the meta-data which is not representable in the 1988 version of ASN.1 but instead is part of the text. In keeping with the current policy of the PKIX working group, the 1988 module and the text is the normative module. In the event of a conflict between the contents of the two modules, the 1988 module is authoritative. When reading this document, it is assumed that you will have a degree of familiarity with the basic object module that is presented in Schaad Expires October 26, 2012 [Page 3] Internet-Draft PubKey Caps April 2012 section 3 of RFC 5912 ([RFC5912]). We use the SMIME-CAPS object in this document, it associates two fields together in a single object. SMIME-CAPS ::= CLASS { &id OBJECT IDENTIFIER UNIQUE, &Type OPTIONAL } WITH SYNTAX { [TYPE &Type] IDENTIFIED BY &id } These fields are: &id contains an object identifier. When placed in an object set, this element is tagged so that no two elements can be placed in the set that have the same value in the &id field. Note that this is not a restriction which says that only a single object can exist with a single object identifier. &Type optionally contains an ASN.1 type identifier. If the field &Type is not defined then the optional parameters field of the AlgorithmIdentifier type would be omitted. The class also has a specialized syntax for how to define an object in this class. The all upper case words TYPE IDENTIFIER and BY are syntactic sugar to make it easier to read. The square brackets define optional pieces of the syntax. One of the things that can be done is to reference the fields of an object while defining other objects. This means that if an object called foo has a field named &value, the value can be directly referenced as foo.&value. This means that we automatically get any updates to values or types and we do not need to do any replication of the data. 1.2. Requirements Terminology When capitalized the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Schaad Expires October 26, 2012 [Page 4] Internet-Draft PubKey Caps April 2012 2. RSA Public Keys There are currently three different public key object identifiers for RSA public keys. These are RSA, RSA ES-OAEP and RSA SSA-PSS. 2.1. Generic RSA Public Keys Almost all RSA keys that are contained in certificates today use the generic RSA public key format and identifier. This allows for the public key to be used both for key transport and for signature validation (assuming it is compatible with the bits in the key usage extension). The only reason for using one of more specific public key identifiers is if the user wants to restrict the usage of the RSA public key to a specific algorithm. For the generic RSA public key, the S/MIME capability that is advertised is a request for a specific key size to be used. This would normally be used for dealing with a request on the key to be used for a signature that the client would then verify. In general the user would provide a specific key when a key transport algorithm is being considered. The ASN.1 that is used for the generic RSA public key is defined as below: scap-pk-rsa SMIME-CAPS ::= { TYPE RSAKeyCapabilities IDENTIFIED BY pk-rsa.&id } RSAKeyCapabilities ::= SEQUENCE { minKeySize RSAKeySize, maxKeySize RSAKeySize OPTIONAL } RSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 | 4096 | 8192, ...) In the above ASN.1 we have defined the following: scap-pk-rsa is a new SMIME-CAP object. This object associates the existing object identifier (rsaEncryption) used for the public key in certificates (defined in [RFC3279] and [RFC5912]) with a new type defined in this document. Schaad Expires October 26, 2012 [Page 5] Internet-Draft PubKey Caps April 2012 RSAKeyCapabilities carries the set of desired capabilities for an RSA key. The fields of this type are: minKeySize contains the minimum length of the RSA modulus to be used. This field SHOULD NOT contain a value less than 1024. maxKeySize contains the maximum length of the RSA modules that should be used. If this field is absent then no maximum length is requested/expected. This value is normally selected so as not to cause the current code to run unacceptably long when processing signatures. RSAKeySize provides a set of suggested values to be used. The values 1024, 2048, 3072, 7680 and 15360 are from the NIST guide on signature sizes [NIST-SIZES] while the others are common powers of two that would be used. The list is not closed and other values can be used. 2.2. RSASSA-PSS Signature Public Keys While most of the time one will use the generic RSA public key identifier in a certificate, the RSA SSA-PSS identifier can be used if the owner of the key desires to restrict the usage of the key to just this algorithm. This algorithm does have the ability to place a set of algorithm parameters in the public key info structure, they have not been included in this location as the same information should be carried in the signature S/MIME capabilities instead. The ASN.1 that is used for the RSA SSA-PSS public key is defined below: scap-pk-rsaSSA-PSS SMIME-CAPS ::= { TYPE RSAKeyCapabilities IDENTIFIED BY pk-rsaSSA-PSS.&id } In the above ASN.1 we have defined the following: scap-pk-rsaSSA-PSS is a new SMIME-CAP object. This object associates the existing object identifier (id-RSASSA-PSS) used for the public key certificates (defined in [RFC4055] and [RFC5912]) with type RSAKeyCapabilities. 2.3. RSA ES-OAEP Key Transport Public Keys While most of the time one will use the generic RSA public key identifier in a certificate, the RSA ES-OAEP identifier can be used if the owner of the key desires to restrict the usage of the key to Schaad Expires October 26, 2012 [Page 6] Internet-Draft PubKey Caps April 2012 just this algorithm. This algorithm does have the ability to place a set of algorithm parameters in the public key info structure, they have not been included in this location as the same information should be carried in the key transport S/MIME capabilities instead. The ASN.1 that is used for the RSA ES-OAEP public key is defined below: scap-pk-rsaES-OAEP SMIME-CAPS ::= { TYPE RSAKeyCapabilities IDENTIFIED BY pk-rsaES-OAEP.&id } In the above ASN.1 we have defined the following: scap-pk-rsaES-OAEP is a new SMIME-CAP object. This object associates the existing object identifier (id-RSAES-OAEP) used for the public key certificates (defined in [RFC4055] and [RFC5912]) with type RSAKeyCapabilities. Schaad Expires October 26, 2012 [Page 7] Internet-Draft PubKey Caps April 2012 3. Diffie-Hellman Keys There are current two Diffie-Hellman public key object identifiers. These are DH key agreement and DSA. 3.1. DSA Signature Public Key This public key type is used for the validation of DSA signatures. The ASN.1 that is used for DSA keys is defined below: scap-pk-dsa SMIME-CAPS ::= { TYPE DSAKeyCapabilities IDENTIFIED BY pk-dsa.&id } DSAKeyCapabilities ::= CHOICE { keySizes [0] SEQUENCE { minKeySize DSAKeySize, maxKeySize DSAKeySize OPTIONAL }, keyParams [1] pk-dsa.&Params } DSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 ) In the above ASN.1 we have defined the following: scap-pk-dsa is a new SMIME-CAP object. This object associates the existing object identifier (id-dsa) used for the public key in certificates (defined in [RFC3279] and [RFC5912]) with a new type defined here, DSAKeyCapabilities. DSAKeyCapabilities carries the desired set of capabilities for the DSA key. The fields of this type are: keySizes is used when only a key size is needed to be specified and not a specific group. It is expected that this would be the most commonly used of the two options. In key sizes the fields are used as follows: minKeySize contains the minimum length of the DSA modulus to be used. maxKeySize contains the maximum length of the DSA modules that should be used. If this field is absent then no maximum length is requested/expected. Schaad Expires October 26, 2012 [Page 8] Internet-Draft PubKey Caps April 2012 keyParams contains the exact set of DSA for the key used to sign the message. This field is provided for completeness and to match the fields for Elliptical Curve, however it is expected that usage of this field is extremely rare. 3.2. DH Key Agreement Keys This public key type is used with the Diffie-Hellman key agreement algorithm. The ASN.1 that is used for DH keys is defined below: scap-pk-dh SMIME-CAPS ::= { TYPE DSAKeyCapabilities IDENTIFIED BY pk-dh.&id } In the above ASN.1 we have defined the following: scap-pk-dh is a new SMIME-CAP object. This object associates the existing object identifier (id-dh) used for the public key algorithm in the certificates (defined in [RFC3279] and [RFC5912]) with a new type defined above, DSAKeyCapabilities. Schaad Expires October 26, 2012 [Page 9] Internet-Draft PubKey Caps April 2012 4. Elliptical Curve Keys There are currently three Elliptical Curve public key object identifiers. These are EC, EC-DH and EC-MQV 4.1. Generic Elliptical Curve Keys Almost all ECC keys that are contained in certificates today use the generic ECC public key format and identifier. This allows for the public key to be used both for key agreement and for signature validation (assuming the appropriate bits are in the certificate). The only reason for using one of the more specific public key identifier is if the user wants to restrict the usage of the ECC public key to a specific algorithm. For the generic ECC public key, the S/MIME capability that is advertised is a request for a specific group to be used. The ASN.1 that is used for the generic ECC public key is defined as below: scap-pk-ec SMIME-CAPS ::= { TYPE EC-SMimeCaps IDENTIFIED BY pk-ec.&id } EC-SMimeCaps ::= SEQUENCE (SIZE (1..MAX)) OF ECParameters In the above ASN.1 we have defined the following: scap-pk-ec is a new SMIME-CAP object. This object associates the existing object identifier (id-ecPublicKey) used for the public key algorithm in the certificates (defined in [RFC3279] and [RFC5912]) with the new type EC-SMimeCaps. EC-SMimeCaps carries a sequence of at least one ECParameters structure. This allows for multiple curves to be requested in a single capability request. A maximum/minimum style of specifying sizes is not provided as much greater care is required in selecting a specific curve than is needed to create the parameters for a DSA/DH key. As specified in [RFC3279], for PKIX compliant certificates only the namedCurve choice of ECParameters is expected to be used. Schaad Expires October 26, 2012 [Page 10] Internet-Draft PubKey Caps April 2012 4.2. Elliptical Curve DH Keys This public key type is used with the Elliptical Curve Diffie-Hellman key agreement algorithm. The ASN.1 that is used for EC-DH keys is defined below: scap-pk-ecDH SMIME-CAPS ::= { TYPE EC-SMimeCaps IDENTIFIED BY pk-ecDH.&id } In the above ASN.1 we have defined the following: scap-ec-dh is a new SMIME-CAP object. This object associates the existing object identifier (id-ecDH) used for the public key algorithm in the certificate (defined in [RFC3279] and [RFC5912]) with the same type structure used for public keys. 4.3. Elliptical Curve MQV Keys This public key type is used with the Elliptical Curve MQV key agreement algorithm. The ASN.1 that is used for EC-MQV keys is defined below: scap-pk-ecMQV SMIME-CAPS ::= { TYPE EC-SMimeCaps IDENTIFIED BY pk-ecMQV.&id } In the above ASN.1 we have defined the following: scap-ec-MQV is a new SMIME-CAP object. This object associates the existing object identifier (id-eqMQV) used for the public key algorithm in the certificate (defined in [RFC3279] and [RFC5912]) with the same type structure used for public keys. Schaad Expires October 26, 2012 [Page 11] Internet-Draft PubKey Caps April 2012 5. RSASSA-PSS Signature Algorithm Capability This document defines a new S/MIME Capability for the RSASSA-PSS signature algorithm. There already exists one in [RFC4055] where the parameters field is not used. When the S/MIME group defined a S/MIME Capability for the RSASSA-PSS signature algorithm, it was done in the context of how S/MIME defines and uses S/MIME Capabilities. When placed in an S/MIME message [SMIME-MSG] or in a certificate [RFC4262] it is always placed in a sequence of capabilities. This means that one could place the identifier for RSASSA-PSS in the sequence along with the identifier for MD5, SHA-1 and SHA-256. The assumption was then made that one could compute the matrix of all answers and the publisher would support all elements in the matrix. This has the possibility that the publisher could accidently publish a point in the matrix that is not supported. In this situation, there is only a single item that is published. This means that we need to publish all of the associated information along with the identifier for the signature algorithm in a single entity. For this reason we now define a new parameter type to be used as the S/MIME capability type which contains a hash identifier and a mask identifier. The ASN.1 used for this is as follows: scap-sa-rsaSSA-PSS SMIME-CAPS ::= { TYPE RsaSsa-Pss-sig-caps IDENTIFIED BY sa-rsaSSA-PSS.&id } RsaSsa-Pss-sig-caps ::= SEQUENCE { hashAlg SMIMECapability{{ HashAlgorithms }}, maskAlg SMIMECapability{{ MaskAlgorithmSet }} OPTIONAL, trailerField INTEGER DEFAULT 1 } scap-mf-mgf1 SMIME-CAPS ::= { TYPE SMIMECapability{{ HashAlgorithms }} IDENTIFIED BY id-mgf1 } MaskAlgorithmSet SMIME-CAPS ::= {scap-mf-mgf1, ...} In the above ASN.1 we have defined the following: Schaad Expires October 26, 2012 [Page 12] Internet-Draft PubKey Caps April 2012 scap-sa-rsaSSA-PSS is a new SMIME-CAP object. This object associates the existing object identifier (id-RSASSA-PSS) used for the signature algorithm (defined in [RFC4055] and [RFC5912]) with the new type RsaSsa-Pss-sig-caps. RsaSsa-Pss-sig-caps carries the desired set of capabilities for the RSA SSA-PSS signature algorithm. The fields of this type are: hashAlg contains the S/MIME capability for the hash algorithm we are declaring we support with the RSASSA-PSS signature algorithm. maskAlg contains the S/MIME capability for the mask algorithm we are declaring we support with the RSASSA-PSS signature algorithm. trailerField specifies which trailer field algorithm is being supported. This MUST be the value 1. NOTE: In at least one iteration of the design we used a sequence of hash identifiers and a sequence of masking functions and again made the assumption that entire the matrix would be supported. This has been removed at this point since the original intent of S/MIME capabilities is that one should be able to do a binary comparison of the DER encoding of the field and determine a specific capability was published. We could return back to using the sequence if we wanted to lose the ability to do a binary compare but needed to shorten the encodings. This does not currently appear to be an issue at this point. Schaad Expires October 26, 2012 [Page 13] Internet-Draft PubKey Caps April 2012 6. Security Considerations This document provides new fields that can be placed in an S/MIME capabilities sequence. There are number of considerations that need to be taken into account when doing this. As mentioned above, we have defined data structures to be associated with Object Identifiers in cases where an association already exists. When either encoding or decoding structures, care needs to be taken that the association used is one appropriate for the location in the surrounding ASN.1 structure. This means that one needs to make sure that only public keys are place in public key locations, signatures are placed in signature locations and S/MIME capabilities are placed in S/MIME Capability locations. Failure to do so at best will create decode errors and at worst can cause incorrect behavior. The more specific the information that is provided in an S/MIME Capabilities field, the better the end results are going to be. Specifying a signature algorithm means that there are no questions for the receiver that the signature algorithm is supported. Signature algorithms can be implied by specifying both public key algorithms and hash algorithms together. If the list includes RSA v1.5, EC-DSA, SHA-1 and SHA-256, the implication is that all four values in the cross section are supported by the sender. If the sender does not support EC-DSA with SHA-1, this would lead to a situation where the recipient uses a signature algorithm that the sender does not support. Omitting SHA-1 from the list may lead to the problem where both entities support RSA v1.5 with SHA-1 as their only common algorithm, but this is no longer discoverable by the recipient. As a general rule, providing more information about the algorithms that are supported is preferable. The more choices that are provided the recipient, the greater the likelihood that a common algorithm with good security can be used by both parties. One should avoid being exhaustive in providing the list of algorithms to the recipient however. The greater the number of algorithms that are passed the more difficult it is for a recipient to make intellegent decisions about which algorithm to be used. This is a more significant problem when there are more than two entities involved in the "negotiation" of a common algorithm to be used (such as sending an encrypted S/MIME message where a common content encryption algorithm is needed). The larger the set of algorithms and the more recipients involved, the more memory and processing time will be needed in order to complete the decision making process. The S/MIME capabilities is defined so that the order of algorithms in the sequence is meant to encode a preference order by the sender of Schaad Expires October 26, 2012 [Page 14] Internet-Draft PubKey Caps April 2012 the sequence. Many entities will ignore the order preference when making a decision either by using their own preferred order or using a random decision from a matrix. Schaad Expires October 26, 2012 [Page 15] Internet-Draft PubKey Caps April 2012 7. IANA Considerations This document has no IANA considerations. Schaad Expires October 26, 2012 [Page 16] Internet-Draft PubKey Caps April 2012 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3279, April 2002. [RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional Algorithms and Identifiers for RSA Cryptography for use in the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 4055, June 2005. 8.2. Informative References [RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the Public Key Infrastructure Using X.509 (PKIX)", RFC 5912, June 2010. [RFC6277] Santesson, S. and P. Hallam-Baker, "Online Certificate Status Protocol Algorithm Agility", RFC 6277, June 2011. [SMIME-MSG] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message Specification", RFC 5751, January 2010. [RFC4262] Santesson, S., "X.509 Certificate Extension for Secure/ Multipurpose Internet Mail Extensions (S/MIME) Capabilities", RFC 4262, December 2005. [SMIMEv3-MSG] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC 2633, June 1999. [NIST-SIZES] Barker, E., Barker, W., Burr, W., Polk, W., and M. Smid, "Recommendation for Key Management -- Part 1: General", NIST Special Publication 800-57, March 2007. Schaad Expires October 26, 2012 [Page 17] Internet-Draft PubKey Caps April 2012 Appendix A. 2008 ASN.1 Module This appendix contains a module compatible with the work done to update the PKIX ASN.1 modules to recent versions of the ASN.1 specifications [RFC5912]. This appendix is to be considered informational per the current direction of the PKIX working group. PUBLIC-KEY-SMIME-CAPABILITIES { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) TBD5 } DEFINITIONS ::= BEGIN IMPORTS SMIME-CAPS, PUBLIC-KEY, SMIMECapability FROM AlgoritrithmInformation-2009 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-algorithmInformation-02(58)} pk-rsa, pk-dsa, pk-dh, pk-ec, pk-ecDH, pk-ecMQV, ECParameters FROM PKIXAlgs-2009 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-algorithms2008-02(56) } pk-rsaSSA-PSS, pk-rsaES-OAEP, sa-rsaSSA-PSS, HashAlgorithms, id-mgf1 FROM PKIX1-PSS-OAEP-Algorithms-2009 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-rsa-pkalgs-02(54)} ; -- -- Define a set containing all of the S/MIME capabilties defined -- by this document -- SMimeCaps SMIME-CAPS ::= { PubKeys-SMimeCaps | scap-sa-rsaSSA-PSS } PubKeys-SMimeCaps SMIME-CAPS ::= { scap-pk-rsa | scap-pk-rsaSSA-PSS | scap-pk-dsa | scap-pk-ec | scap-pk-ecDH } Schaad Expires October 26, 2012 [Page 18] Internet-Draft PubKey Caps April 2012 -- -- We defined RSA keys from the modules RFC3279 and RFC4055 -- scap-pk-rsa SMIME-CAPS ::= { TYPE RSAKeyCapabilities IDENTIFIED BY pk-rsa.&id } RSAKeyCapabilities ::= SEQUENCE { minKeySize RSAKeySize, maxKeySize RSAKeySize OPTIONAL } RSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 | 4096 | 8192, ...) scap-pk-rsaES-OAEP SMIME-CAPS ::= { TYPE RSAKeyCapabilities IDENTIFIED BY pk-rsaES-OAEP.&id } scap-pk-rsaSSA-PSS SMIME-CAPS ::= { TYPE RSAKeyCapabilities IDENTIFIED BY pk-rsaSSA-PSS.&id } scap-sa-rsaSSA-PSS SMIME-CAPS ::= { TYPE RsaSsa-Pss-sig-caps IDENTIFIED BY sa-rsaSSA-PSS.&id } RsaSsa-Pss-sig-caps ::= SEQUENCE { hashAlg SMIMECapability{{ HashAlgorithms }}, maskAlg SMIMECapability{{ MaskAlgorithmSet }} OPTIONAL, trailerField INTEGER DEFAULT 1 } scap-mf-mgf1 SMIME-CAPS ::= { TYPE SMIMECapability{{ HashAlgorithms }} IDENTIFIED BY id-mgf1 } MaskAlgorithmSet SMIME-CAPS ::= {scap-mf-mgf1, ...} -- -- we define DH/DSA keys from the module RFC3279 Schaad Expires October 26, 2012 [Page 19] Internet-Draft PubKey Caps April 2012 -- scap-pk-dsa SMIME-CAPS ::= { TYPE DSAKeyCapabilities IDENTIFIED BY pk-dsa.&id } DSAKeyCapabilities ::= CHOICE { keySizes [0] SEQUENCE { minKeySize DSAKeySize, maxKeySize DSAKeySize OPTIONAL }, keyParams [1] pk-dsa.&Params } DSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 ) scap-pk-dh SMIME-CAPS ::= { TYPE DSAKeyCapabilities IDENTIFIED BY pk-dh.&id } -- -- we define Eliptical Curve keys from the module RFC3279 -- scap-pk-ec SMIME-CAPS ::= { TYPE EC-SMimeCaps IDENTIFIED BY pk-ec.&id } EC-SMimeCaps ::= SEQUENCE (SIZE (1..MAX)) OF ECParameters scap-pk-ecDH SMIME-CAPS ::= { TYPE EC-SMimeCaps IDENTIFIED BY pk-ecDH.&id } scap-pk-ecMQV SMIME-CAPS ::= { TYPE EC-SMimeCaps IDENTIFIED BY pk-ecMQV.&id } END Schaad Expires October 26, 2012 [Page 20] Internet-Draft PubKey Caps April 2012 Appendix B. 1988 ASN.1 Module This appendix contains the normative ASN.1 module for this document. PUBLIC-KEY-SMIME-CAPABILITIES-88 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) TBD5 } DEFINITIONS ::= BEGIN IMPORTS ECParameters FROM PKIX1Algorithms88 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-algorithms(17) } id-mgf1 FROM PKIX1-PSS-OAEP-Algorithms { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-rsa-pkalgs(33) } AlgorithmIdentifier FROM PKIX1Explicit88 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit(18) } ; -- -- We defined RSA keys from the modules RFC3279 and RFC4055 -- RSAKeyCapabilities ::= SEQUENCE { minKeySize RSAKeySize, maxKeySize RSAKeySize OPTIONAL } RSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 | 4096 | 8192, ...) RsaSsa-Pss-sig-caps ::= SEQUENCE { hashAlg AlgorithmIdentifier, maskAlg AlgorithmIdentifier OPTIONAL, trailerField INTEGER DEFAULT 1 Schaad Expires October 26, 2012 [Page 21] Internet-Draft PubKey Caps April 2012 } -- -- we define DH/DSA keys from the module RFC3279 -- DSAKeyCapabilities ::= CHOICE { keySizes [0] SEQUENCE { minKeySize DSAKeySize, maxKeySize DSAKeySize OPTIONAL }, keyParams [1] pk-dsa.&Params } DSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 ) -- -- we define Eliptical Curve keys from the module RFC3279 -- EC-SMimeCaps ::= SEQUENCE (SIZE (1..MAX)) OF ECParameters END Schaad Expires October 26, 2012 [Page 22] Internet-Draft PubKey Caps April 2012 Appendix C. Future Work A future revision of [RFC5912] should be done at some point which expands the definition of the PUBLIC-KEY class and allows for an S/MIME Capability to be included in the class definition. This would encourage people to think about this as an issue when defining new public key structures in the future. Schaad Expires October 26, 2012 [Page 23] Internet-Draft PubKey Caps April 2012 Author's Address Jim Schaad Soaring Hawk Consulting Email: ietf@augustcellars.com Schaad Expires October 26, 2012 [Page 24]