Network Working Group S. Raza Internet-Draft J. Hoeglund Intended status: Standards Track RISE AB Expires: May 28, 2021 G. Selander J. Mattsson Ericsson AB M. Furuhed Nexus Group November 24, 2020 CBOR Encoding of X.509 Certificates (CBOR Certificates) draft-mattsson-cose-cbor-cert-compress-04 Abstract This document specifies a CBOR encoding of PKIX profiled X.509 Certificates. The resulting certificates are called "CBOR certificates". The CBOR encoding supports a large subset of RFC 5280, while at the same time producing very small sizes for certificates compatible with RFC 7925. The CBOR encoding can be used to compress DER encoded X.509 certificates and to encode natively signed certificates. When uses to compress DER encoded X.509 certificates, the CBOR encoding can in many cases compress RFC 7925 profiled certificates with over 50%. The document also specifies COSE headers for CBOR certificates as well as a TLS certificate type for CBOR certificates. 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 https://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 May 28, 2021. Raza, et al. Expires May 28, 2021 [Page 1] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 Copyright Notice Copyright (c) 2020 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 (https://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 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . 4 3. CBOR Encoding . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Message Fields . . . . . . . . . . . . . . . . . . . . . 5 3.2. Encoding of Extensions . . . . . . . . . . . . . . . . . 8 4. Compliance Requirements for Constrained IoT . . . . . . . . . 10 5. Deployment settings . . . . . . . . . . . . . . . . . . . . . 10 6. Expected Certificate Sizes . . . . . . . . . . . . . . . . . 11 7. Natively Signed CBOR Certificates . . . . . . . . . . . . . . 11 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 9.1. CBOR Certificate Types Registry . . . . . . . . . . . . . 12 9.2. CBOR Attribute Type Registry . . . . . . . . . . . . . . 12 9.3. CBOR Extension Type Registry . . . . . . . . . . . . . . 13 9.4. CBOR Extended Key Usage Registry . . . . . . . . . . . . 14 9.5. CBOR Subject Alternative Name Registry . . . . . . . . . 15 9.6. CBOR Certificate Signature Algorithms Registry . . . . . 15 9.7. CBOR Certificate Public Key Algorithms Registry . . . . . 16 9.8. COSE Header Parameters Registry . . . . . . . . . . . . . 17 9.9. TLS Certificate Types Registry . . . . . . . . . . . . . 18 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 10.1. Normative References . . . . . . . . . . . . . . . . . . 18 10.2. Informative References . . . . . . . . . . . . . . . . . 19 Appendix A. Example CBOR Certificates . . . . . . . . . . . . . 20 A.1. Example RFC 7925 profiled X.509 Certificate . . . . . . . 20 A.2. Example HTPPS X.509 Certificate . . . . . . . . . . . . . 23 Appendix B. X.509 Certificate Profile, ASN.1 . . . . . . . . . . 26 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 28 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28 Raza, et al. Expires May 28, 2021 [Page 2] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 1. Introduction One of the challenges with deploying a Public Key Infrastructure (PKI) for the Internet of Things (IoT) is the size and encoding of X.509 public key certificates [RFC5280], since those are not optimized for constrained environments [RFC7228]. More compact certificate representations are desirable. Due to the current PKI usage of DER encoded X.509 certificates, keeping compatibility with DER encoded X.509 is necessary at least for a transition period. However, the use of a more compact encoding with the Concise Binary Object Representation (CBOR) [RFC7049] reduces the certificate size significantly which has known performance benefits in terms of decreased communication overhead, power consumption, latency, storage, etc. CBOR is a data format designed for small code size and small message size. CBOR builds on the JSON data model but extends it by e.g. encoding binary data directly without base64 conversion. In addition to the binary CBOR encoding, CBOR also has a diagnostic notation that is readable and editable by humans. The Concise Data Definition Language (CDDL) [RFC8610] provides a way to express structures for protocol messages and APIs that use CBOR. [RFC8610] also extends the diagnostic notation. CBOR data items are encoded to or decoded from byte strings using a type-length-value encoding scheme, where the three highest order bits of the initial byte contain information about the major type. CBOR supports several different types of data items, in addition to integers (int, uint), simple values (e.g. null), byte strings (bstr), and text strings (tstr), CBOR also supports arrays [] of data items, maps {} of pairs of data items, and sequences of data items. For a complete specification and examples, see [RFC7049], [RFC8610], and [RFC8742]. RFC 7925 [RFC7925] specifies a certificate profile for Internet of Things deployments which can be applied for lightweight certificate based authentication with e.g. TLS [RFC8446], DTLS [I-D.ietf-tls-dtls13], COSE [RFC8152], or EDHOC [I-D.ietf-lake-edhoc]. This document specifies a CBOR encoding which can support large parts of [RFC5280] based on [X.509-IoT]. The encoding support all [RFC7925] profiled X.509 certificates. Two variants are defined using the same CBOR encoding and differing only in what is being signed: o CBOR compression of DER encoded X.509 certificates [RFC5280], which can be decompressed into the original DER encoded X.509 certificate. Raza, et al. Expires May 28, 2021 [Page 3] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 o Natively signed CBOR certificates, which further optimizes the performance in constrained environments but is not backwards compatible with [RFC5280], see Section 7. This document specifies COSE headers for use of the CBOR certificates with COSE, see Section 9.8. The document also specifies a TLS certificate type for use of the CBOR certificates with TLS (with or without additional TLS certificate compression), see Section 9.9. 2. Notational Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. This specification makes use of the terminology in [RFC5280], [RFC7049], [RFC7228], and [RFC8610]. 3. CBOR Encoding This section specifies the content and encoding for CBOR certificates, with the overall objective to produce a very compact representation supporting large parts of [RFC5280] and everything in [RFC7925]. In the CBOR encoding, static fields are elided, elliptic curve points are compressed, OID are replaced with short integers, time values are compressed, and redundant encoding is removed. Combining these different components reduces the certificate size significantly, which is not possible with general purpose compressions algorithms, see Figure 1. The CBOR certificate can be either a CBOR compressed X.509 certificate, in which case the signature is calculated on the DER encoded ASN.1 data in the X.509 certificate, or a natively signed CBOR certificate, in which case the signature is calculated directly on the CBOR encoded data (see Section 7). In both cases the certificate content is adhering to the restrictions given by [RFC5280]. When used as for compression of an existing X.509 certificate, the encoding only works on canonical encoded certificates. The encoding is known to work with DER but might work with other canonical encodings. The compression does not work for BER encoded certificates. In the encoding described below the order of elements in arrays are always encoded in the same order as the elements or the corresponding SEQUENCE or SET in the DER encoding. Raza, et al. Expires May 28, 2021 [Page 4] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 3.1. Message Fields The X.509 fields and their CBOR encodings are listed below. CBOR certificates are defined in terms of DER encoded [RFC5280] X.509 certificates: o version. The 'version' field is known (fixed to v3) and is omitted in the CBOR encoding. o serialNumber. The 'serialNumber' INTEGER value field is encoded as the unwrapped CBOR positive bignum (~biguint) 'certificateSerialNumber'. Any leading 0x00 byte (to indicate that the number is not negative) is therefore omitted. o signatureAlgorithm. The 'signatureAlgorithm' field is encoded as a CBOR int 'issuerSignatureAlgorithm' (see Section 9.6) or a CBOR OID tag [I-D.ietf-cbor-tags-oid]. Algorithms with parameters are not supported except RSA algorithms that use parameters = NULL. o signature. The 'signature' field is always the same as the 'signatureAlgorithm' field and always omitted from the CBOR encoding. o issuer. In the general case, the sequence of 'RelativeDistinguishedName' is encoded as CBOR array of CBOR arrays of Attributes, where each Attribute type and value is encoded as a (CBOR int, CBOR text string) pair. Each AttributeType is encoded as a CBOR int (see Figure 3), where the sign is used to represent the character string type; positive for printableString, negative for utf8String. The string types teletexString, universalString, and bmpString are not supported. If Name contains a single Attribute containing an utf8String encoded 'common name' it is encoded as a CBOR text string. If the text string contains an EUI-64 of the form "HH-HH-HH-HH-HH-HH-HH- HH" where 'H' is one of the symbol '0'-'9' or 'A'-'F' it is encoded as a CBOR byte string of length 8 instead. EUI-64 mapped from a 48-bit MAC address (i.e. of the form "HH-HH-HH-FF-FE-HH-HH- HH) is encoded as a CBOR byte string of length 6. o validity. The 'notBefore' and 'notAfter' fields are ASCII string of the form "yymmddHHMMSSZ" for UTCTime and "yyyymmddHHMMSSZ" for GeneralizedTime. They ASCII strings are converted to integers using the following invertible encoding (Horner's method with different bases). n = SS + 61 * (MM + 60 * (HH + 24 * (dd + 32 * (mm + 13 * (yy)yy)))) Raza, et al. Expires May 28, 2021 [Page 5] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 The integer n is encoded as the unwrapped CBOR positive bignum (~biguint). GeneralizedTime before the year 100 AD is not supported. Decoding can be done by a succession of modulo and subtraction operations. I.e. SS = n mod 61, MM = ((n - SS) / 61) mod 60, etc. o subject. The 'subject' is encoded exactly like issuer. o subjectPublicKeyInfo. The 'algorithm' field is encoded as the CBOR int 'subjectPublicKeyAlgorithm' (see Section 9.7) or a CBOR OID tag [I-D.ietf-cbor-tags-oid] . Algorithms with parameters are not supported except id-ecPublicKey with named curves and the RSA algorithms that use parameters = NULL. For id-ecPublicKey the namedCurve parameter is encoded in the CBOR int. The 'subjectPublicKey' BIT STRING value field is encoded as a CBOR byte string. This specification assumes the BIT STRING has zero unused bits and the unused bits byte is omitted. Uncompressed public keys of type id-ecPublicKey are point compressed as defined in Section 2.3.3 of [SECG]. If a DER encoded certificate with a point compressed public key of type id-ecPublicKey is CBOR encoded, the octets 0xfe and 0xfd are used instead of 0x02 and 0x03 in the CBOR encoding to represent an even and odd y-coordinate respectively. o extensions. The 'extensions' field is encoded as a CBOR array where each extension is encoded as either a CBOR int (see Section 9.3) followed by an optional CBOR item of any type or a CBOR OID tag [I-D.ietf-cbor-tags-oid] followed by a CBOR bool encoding 'critical' and the DER encoded value of the 'extnValue' encoded as a CBOR byte string. If the array contains exactly two ints and the absolute value of the first int is 2, the array is omitted and the extensions is encoded as a single CBOR int with the absolute value of the second int and the sign of the first int. Extensions are encoded as specified in Section 3.2. The extensions mandated to be supported by [RFC7925] are given special treatment. o signatureValue. The 'signatureValue' BIT STRING value field is encoded as the CBOR byte string issuerSignatureValue. This specification assumes the BIT STRING has zero unused bits and the unused bits byte is omitted. ECDSA signatures are given special treatment. For ECDSA signatures the SEQUENCE and INTEGER type and length fields are omitted and the two INTEGER value fields are padded to the fixed length L = ceil( log2(n) / 8 ), where n is the size of the largest prime-order subgroup. For secp256r1, secp384r1, and secp521r1, L is 32, 48, and 66 respectively. For natively signed CBOR certificates the signatureValue is calculated over the CBOR sequence TBSCertificate. Raza, et al. Expires May 28, 2021 [Page 6] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 In addition to the above fields present in X.509, the CBOR encoding introduces an additional field: o cborCertificateType. A CBOR int used to indicate the type of CBOR certificate. Currently, type can be a natively signed CBOR certificate (cborCertificateType = 0) or a CBOR compressed X.509 v3 certificate (cborCertificateType = 1), see Section 9.1. The following Concise Data Definition Language (CDDL) defines CBORCertificate and TBSCertificate, which are encoded as CBOR Sequences [RFC8742]. The member names therefore only have documentary value. Raza, et al. Expires May 28, 2021 [Page 7] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 ; This defines an array, the elements of which are to be used in a CBOR Sequence: CBORCertificate = [ TBSCertificate, issuerSignatureValue : bytes, ] TBSCertificate = ( cborCertificateType : int, certificateSerialNumber : ~biguint, issuerSignatureAlgorithm : Algorithm, issuer : Name, validityNotBefore : ~biguint, validityNotAfter : ~biguint, subject : Name, subjectPublicKeyAlgorithm : Algorithm, subjectPublicKey : bytes, extensions : Extensions, ) Algorithm = int / OID OID = #6.6(bstr) ; tag number 6 is used here, but tag number is TBD Name = [ * [ + Attribute ] ] / text / bytes Attribute = ( attributeType : int, attributeValue : text, ) Extensions = [ * Extension ] / int, Extension = ( extensionID : int / OID, ? critical : bool, ; present if and only if extensionID is an OID extensionValue : any, ; type known from extensionType ) 3.2. Encoding of Extensions EDITOR'S NOTE: The current specification encodes many common extensions with a DER encoded byte string. It should be discussed if more or all commonly active extensions should be natively encoded with CBOR. Would a specific CBOR encoding have to be specified for each extension or can a general CBOR encoding that apply to all remaining extensions be specified? Raza, et al. Expires May 28, 2021 [Page 8] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 This section details the encoding of the 'extensions' field. The 'extensions' field is encoded as a CBOR array where each extensionID is encoded as either a CBOR int or a CBOR OID tag. If 'extensionID' is encoded an int (see Section 9.3),the sign is used to encode if the extension is critical and the 'critical' field is omitted. Critical extensions are encoded with a positive sign and non-critical extensions are encoded with a negative sign. The 'extnValue' OCTET STREAM value field is encoded as the CBOR byte string 'extensionValue' except for the extensions specified below. The 'extensionValue' for the extensions mandated to be supported by [RFC7925] are encoded as follows: o basicConstraints. If 'cA' = false then extensionValue = -2, if 'cA' = true and 'pathLenConstraint' is not present then extensionValue = -1, and if 'cA' = true and 'pathLenConstraint' is present then extensionValue = pathLenConstraint. o keyUsage. The 'KeyUsage' BIT STRING is interpreted as an unsigned integer n in network byte order and encoded as a CBOR int. o extKeyUsage. extensionValue is encoded as an array of CBOR ints (see Section 9.4) or CBOR OID tags [I-D.ietf-cbor-tags-oid] where each ints or OID tag encodes a key usage purpose. If the array contains a single int, the array is omitted. extensionValue = [ * int / OID ] / int o subjectAltName. extensionValue is encoded as an [ * ( int, any ) ] array where each (int, any) pair encodes a general name (see Section 9.5). If subjectAltName contains exactly one dNSName, the array and the int are omitted and extensionValue is the dNSName encoded as a CBOR text string. 3.2.1. Example Encoding of Extensions The examples below use values from Section 9.3, Section 9.4, and Section 9.5: o A critical basicConstraints ('cA' = true) without pathLenConstraint is encoded as the two CBOR ints -1, -1. o A non-critical keyUsage with digitalSignature and keyAgreement asserted is encoded as the two CBOR ints 2, 17 (2^0 + 2^4 = 17). o A non-critical extKeyUsage containing id-kp-codeSigning and id-kp- OCSPSigning is encoded as the CBOR int 3 followed by the CBOR array [ 3, 6 ]. Raza, et al. Expires May 28, 2021 [Page 9] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 o A non-critical subjectAltName containing only the dNSName example.com is encoded as the CBOR int 4 followed by the CBOR text string "example.com". Thus, the extension field of a certificate containing all of the above extensions in the given order would be encoded as the CBOR array [ -1, -1, 2, 17, 3, [ 3, 6 ], 4, "example.com" ]. 4. Compliance Requirements for Constrained IoT For general purpose applications, the normative requirements of [RFC5280] applies. This section describes the mandatory to implement algorithms and OIDs for constrained IoT application; the values of the OIDs including certificate fields and extensions, time format, attributes in distinguished names, etc. TODO: Write this section 5. Deployment settings CBOR certificates can be deployed with legacy X.509 certificates and CA infrastructure. In order to verify the signature, the CBOR certificate is used to recreate the original X.509 data structure to be able to verify the signature. For protocols like TLS/DTLS 1.2, where the handshake is sent unencrypted, the actual encoding and compression can be done at different locations depending on the deployment setting. For example, the mapping between CBOR certificate and standard X.509 certificate can take place in a 6LoWPAN border gateway which allows the server side to stay unmodified. This case gives the advantage of the low overhead of a CBOR certificate over a constrained wireless links. The conversion to X.509 within an IoT device will incur a computational overhead, however, measured in energy this is negligible compared to the reduced communication overhead. For the setting with constrained server and server-only authentication, the server only needs to be provisioned with the CBOR certificate and does not perform the conversion to X.509. This option is viable when client authentication can be asserted by other means. For protocols like IKEv2, TLS/DTLS 1.3, and EDHOC, where certificates are encrypted, the proposed encoding needs to be done fully end-to- end, through adding the encoding/decoding functionality to the server. Raza, et al. Expires May 28, 2021 [Page 10] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 6. Expected Certificate Sizes The CBOR encoding of the sample certificate given in Appendix A results in the numbers shown in Figure 1. After [RFC7925] profiling, most duplicated information has been removed, and the remaining text strings are minimal in size. Therefore, the further size reduction reached with general compression mechanisms will be small, mainly corresponding to making the ASN.1 encoding more compact. The zlib number was calculated with zlib-flate. zlib-flate -compress < cert.der > cert.compressed +------------------+--------------+------------+--------------------+ | | RFC 7925 | zlib | CBOR Certificate | +------------------+---------------------------+--------------------+ | Certificate Size | 314 | 295 | 138 | +------------------+--------------+------------+--------------------+ Figure 1: Comparing Sizes of Certificates (bytes) 7. Natively Signed CBOR Certificates The difference between CBOR compressed X.509 certificate and natively signed CBOR certificate is that the signature is calculated over the CBOR encoding of the CBOR sequence TBSCertficate rather than the DER encoded ASN.1 data. This removes entirely the need for ASN.1 DER and base64 encoding which reduces the processing in the authenticating devices and avoids known complexities with these encoding. Natively signed CBOR certificates can be applied in devices that are only required to authenticate to natively signed CBOR certificate compatible servers. This is not a major restriction for many IoT deployments, where the parties issuing and verifying certificates can be a restricted ecosystem which not necessarily involves public CAs. CBOR compressed X.509 certificates provides an intermediate step between [RFC7925] profiled X.509 certificates and natively signed CBOR certificates: An implementation of CBOR compressed X.509 certificates contains both the CBOR encoding of the X.509 certificate and the signature operations sufficient for natively signed CBOR certificates. The natively signed approach based on DER encoded X.509 certificates described in this document has a lot of benefits. A CA can use existing ASN.1 machinery to create a DER encoded certificate, the DER encoded certificate can then be transformed to CBOR before signing. Raza, et al. Expires May 28, 2021 [Page 11] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 8. Security Considerations The CBOR profiling of X.509 certificates does not change the security assumptions needed when deploying standard X.509 certificates but decreases the number of fields transmitted, which reduces the risk for implementation errors. Conversion between the certificate formats can be made in constant time to reduce risk of information leakage through side channels. The mechanism in this draft does not reveal any additional information compared to X.509. Because of difference in size, it will be possible to detect that this profile is used. The gateway solution described in Section 5 requires unencrypted certificates and is not recommended. 9. IANA Considerations For all items, the 'Reference' field points to this document. 9.1. CBOR Certificate Types Registry IANA has created a new registry titled "CBOR Certificate Types" under the new heading "CBOR Certificate". For values in the interval [-24, 23] the registration procedure is "IETF Review". For all other values the registration procedure is "Expert Review". The columns of the registry are Value, Description, and Reference, where Value is an integer, and the other columns are text strings. The initial contents of the registry are: +-------+---------------------------------------+ | Value | Description | +=======+=======================================+ | 0 | Natively Signed CBOR Certificate | | 1 | CBOR Compressed X.509 v3 Certificate | +-------+---------------------------------------+ Figure 2: CBOR Certificate Types 9.2. CBOR Attribute Type Registry IANA has created a new registry titled "CBOR Attribute Type Registry" under the new heading "CBOR Certificate". The columns of the registry are Value, X.509 Attribute Type, and Reference, where Value is an integer, and the other columns are text strings. Only positive values can be registered. For values in the interval [1, 23] the registration procedure is "IETF Review". For all other values the Raza, et al. Expires May 28, 2021 [Page 12] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 registration procedure is "Expert Review". The initial contents of the registry are: +-------+---------------------------------------+ | Value | X.509 Attribute Type | +=======+=======================================+ | 1 | id-at-commonName | | 2 | id-at-surname | | 3 | id-at-serialNumber | | 4 | id-at-countryName | | 5 | id-at-localityName | | 6 | id-at-stateOrProvinceName | | 7 | id-at-organizationName | | 8 | id-at-organizationalUnitName | | 9 | id-at-title | | 10 | id-at-givenName | | 11 | id-at-initials | | 12 | id-at-generationQualifier | | 13 | id-at-dnQualifier | | 14 | id-at-pseudonym | | 15 | id-at-organizationIdentifier | +-------+---------------------------------------+ Figure 3: CBOR Attribute Type Registry 9.3. CBOR Extension Type Registry IANA has created a new registry titled "CBOR Extension Type Registry" under the new heading "CBOR Certificate". The columns of the registry are Value, X.509 Extension Type, and Reference, where Value is an integer, and the other columns are text strings. Only positive values can be registered. For values in the interval [1, 23] the registration procedure is "IETF Review". For all other values the registration procedure is "Expert Review". The initial contents of the registry are: Raza, et al. Expires May 28, 2021 [Page 13] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 +-------+-------------------------------------+------------------+ | Value | X.509 Extension Type | extensionValue | +=======+=====================================+==================+ | 1 | id-ce-basicConstraints | int | | 2 | id-ce-keyUsage | int | | 3 | id-ce-extKeyUsage | [] / int | | 4 | id-ce-subjectAltName | [] / text | | 5 | id-ce-authorityKeyIdentifier | bytes | | 6 | id-ce-subjectKeyIdentifier | bytes | | 7 | id-ce-certificatePolicies | bytes | | 8 | id-ce-cRLDistributionPoints | bytes | | 9 | id-pe-authorityInfoAccess | bytes | | 10 | SCT List (1.3.6.1.4.1.11129.2.4.2) | bytes | | 248 | id-ce-nameConstraints | bytes | | 249 | id-ce-policyConstraints | bytes | | 250 | id-ce-inhibitAnyPolicy | bytes | | 251 | id-ce-authorityKeyIdentifier | bytes | | 252 | id-ce-policyMappings | bytes | | 253 | id-ce-issuerAltName | bytes | | 254 | id-ce-subjectDirectoryAttributes | bytes | | 255 | id-ce-freshestCRL | bytes | | 256 | id-pe-subjectInfoAccess | bytes | +-------+-------------------------------------+------------------+ Figure 4: CBOR Extension Type Registry 9.4. CBOR Extended Key Usage Registry IANA has created a new registry titled "CBOR Extended Key Usage Registry" under the new heading "CBOR Certificate". The columns of the registry are Value, Extended Key Usage Purpose, and Reference, where Value is an integer, and the other columns are text strings. For values in the interval [-24, 23] the registration procedure is "IETF Review". For all other values the registration procedure is "Expert Review". The initial contents of the registry are: Raza, et al. Expires May 28, 2021 [Page 14] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 +-------+---------------------------------------+ | Value | Extended Key Usage | +=======+=======================================+ | 0 | anyExtendedKeyUsage | | 1 | id-kp-serverAuth | | 2 | id-kp-clientAuth | | 3 | id-kp-codeSigning | | 4 | id-kp-emailProtection | | 5 | id-kp-timeStamping | | 6 | id-kp-OCSPSigning | +-------+---------------------------------------+ Figure 5: CBOR Extended Key Usage Registry 9.5. CBOR Subject Alternative Name Registry IANA has created a new registry titled "CBOR Subject Alternative Name Registry" under the new heading "CBOR Certificate". The columns of the registry are Value, Extended Key Usage Purpose, and Reference, where Value is an integer, and the other columns are text strings. For values in the interval [-24, 23] the registration procedure is "IETF Review". For all other values the registration procedure is "Expert Review". The initial contents of the registry are: +-------+-----------------------------------+------------------+ | Value | Subject Alternative Name | | +=======+===================================+==================+ | 0 | otherName | [ OID, bytes ] | | 1 | rfc822Name | text | | 2 | dNSName | text | | 3 | directoryName | Name | | 4 | uniformResourceIdentifier | text | | 5 | iPAddress | bytes | +-------+-----------------------------------+------------------+ Figure 6: CBOR Subject Alternative Name Registry 9.6. CBOR Certificate Signature Algorithms Registry IANA has created a new registry titled "CBOR Certificate Signature Algorithms" under the new heading "CBOR Certificate". For values in the interval [-24, 23] the registration procedure is "IETF Review". For all other values the registration procedure is "Expert Review". The columns of the registry are Value, X.509 Algorithm, and Reference, where Value is an integer, and the other columns are text strings. The initial contents of the registry are: Raza, et al. Expires May 28, 2021 [Page 15] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 +-------+---------------------------------------+ | Value | X.509 Signature Algorithm | +=======+=======================================+ | 0 | sha1WithRSAEncryption | | 1 | sha256WithRSAEncryption | | 2 | sha384WithRSAEncryption | | 3 | sha512WithRSAEncryption | | 4 | id-RSASSA-PSS-SHAKE128 | | 5 | id-RSASSA-PSS-SHAKE256 | | 6 | ecdsa-with-SHA256 | | 7 | ecdsa-with-SHA384 | | 8 | ecdsa-with-SHA512 | | 9 | id-ecdsa-with-shake128 | | 10 | id-ecdsa-with-shake256 | | 11 | id-Ed25519 | | 12 | id-Ed448 | | 13 | id-alg-hss-lms-hashsig | | 14 | id-alg-xmss | | 15 | id-alg-xmssmt | | 245 | sha224WithRSAEncryption | | 246 | id-rsassa-pkcs1-v1_5-with-sha3-224 | | 247 | id-rsassa-pkcs1-v1_5-with-sha3-256 | | 248 | id-rsassa-pkcs1-v1_5-with-sha3-384 | | 249 | id-rsassa-pkcs1-v1_5-with-sha3-512 | | 250 | ecdsa-with-SHA1 | | 251 | ecdsa-with-SHA224 | | 252 | id-ecdsa-with-sha3-224 | | 253 | id-ecdsa-with-sha3-256 | | 254 | id-ecdsa-with-sha3-384 | | 255 | id-ecdsa-with-sha3-512 | +-------+---------------------------------------+ Figure 7: CBOR Certificate Signature Algorithms 9.7. CBOR Certificate Public Key Algorithms Registry IANA has created a new registry titled "CBOR Certificate Public Key Algorithms" under the new heading "CBOR Certificate". For values in the interval [-24, 23] the registration procedure is "IETF Review". For all other values the registration procedure is "Expert Review". The columns of the registry are Value, X.509 Algorithm, and Reference, where Value is an integer, and the other columns are text strings. The initial contents of the registry are: Raza, et al. Expires May 28, 2021 [Page 16] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 +-------+---------------------------------------+ | Value | X.509 Public Key Algorithm | +=======+=======================================+ | 0 | rsaEncryption | | 1 | id-ecPublicKey + secp256r1 | | 2 | id-ecPublicKey + secp384r1 | | 3 | id-ecPublicKey + secp521r1 | | 4 | id-X25519 | | 5 | id-X448 | | 6 | id-Ed25519 | | 7 | id-Ed448 | | 8 | id-alg-hss-lms-hashsig | | 9 | id-alg-xmss | | 10 | id-alg-xmssmt | +-------+---------------------------------------+ Figure 8: CBOR Certificate Public Key Algorithms 9.8. COSE Header Parameters Registry This document registers the following entries in the "COSE Header Parameters" registry under the "CBOR Object Signing and Encryption (COSE)" heading. The formatting and processing are the same as the corresponding x5bag, x5chain, x5t, and x5u defined in [I-D.ietf-cose-x509] except that the certificates are CBOR encoded instead of DER encoded. Note that certificates can also be identified with a 'kid' header parameter by storing 'kid' and the associated bag or chain in a dictionary. +-----------+-------+----------------+---------------------+ | Name | Label | Value Type | Description | +===========+=======+================+=====================+ | c5bag | TBD1 | COSE_X509 | An unordered bag of | | | | | CBOR certificates | +-----------+-------+----------------+---------------------+ | c5chain | TBD2 | COSE_X509 | An ordered chain of | | | | | CBOR certificates | +-----------+-------+----------------+---------------------+ | c5t | TBD3 | COSE_CertHash | Hash of an | | | | | CBOR certificate | +-----------+-------+----------------+---------------------+ | c5u | TBD4 | uri | URI pointing to a | | | | | CBOR certificate | +-----------+-------+----------------+---------------------+ Raza, et al. Expires May 28, 2021 [Page 17] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 9.9. TLS Certificate Types Registry This document registers the following entry in the "TLS Certificate Types" registry under the "Transport Layer Security (TLS) Extensions" heading. The new certificate type can be used with addtional TLS certificate compression [I-D.ietf-tls-certificate-compression]. EDITOR'S NOTE: The TLS registrations should be discussed and approved by the TLS WG at a later stage. When COSE WG has adopted work on CBOR certificates, it could perhaps be presented in the TLS WG. The TLS WG might e.g. want a separate draft in the TLS WG. +-------+------------------+-------------+---------+ | Value | Name | Recommended | Comment | +=======+==================+=============+=========+ | TBD5 | CBOR Certificate | Y | | +-------+------------------+-------------+---------+ 10. References 10.1. Normative References [I-D.ietf-cbor-tags-oid] Bormann, C. and S. Leonard, "Concise Binary Object Representation (CBOR) Tags for Object Identifiers", draft- ietf-cbor-tags-oid-03 (work in progress), November 2020. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, . [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013, . [RFC7925] Tschofenig, H., Ed. and T. Fossati, "Transport Layer Security (TLS) / Datagram Transport Layer Security (DTLS) Profiles for the Internet of Things", RFC 7925, DOI 10.17487/RFC7925, July 2016, . Raza, et al. Expires May 28, 2021 [Page 18] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 [RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)", RFC 8152, DOI 10.17487/RFC8152, July 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, June 2019, . [RFC8742] Bormann, C., "Concise Binary Object Representation (CBOR) Sequences", RFC 8742, DOI 10.17487/RFC8742, February 2020, . 10.2. Informative References [I-D.ietf-cose-x509] Schaad, J., "CBOR Object Signing and Encryption (COSE): Header parameters for carrying and referencing X.509 certificates", draft-ietf-cose-x509-07 (work in progress), September 2020. [I-D.ietf-lake-edhoc] Selander, G., Mattsson, J., and F. Palombini, "Ephemeral Diffie-Hellman Over COSE (EDHOC)", draft-ietf-lake- edhoc-02 (work in progress), November 2020. [I-D.ietf-tls-certificate-compression] Ghedini, A. and V. Vasiliev, "TLS Certificate Compression", draft-ietf-tls-certificate-compression-10 (work in progress), January 2020. [I-D.ietf-tls-dtls13] Rescorla, E., Tschofenig, H., and N. Modadugu, "The Datagram Transport Layer Security (DTLS) Protocol Version 1.3", draft-ietf-tls-dtls13-39 (work in progress), November 2020. [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for Constrained-Node Networks", RFC 7228, DOI 10.17487/RFC7228, May 2014, . Raza, et al. Expires May 28, 2021 [Page 19] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [SECG] "Elliptic Curve Cryptography, Standards for Efficient Cryptography Group, ver. 2", 2009, . [X.509-IoT] Forsby, F., Furuhed, M., Papadimitratos, P., and S. Raza, "Lightweight X.509 Digital Certificates for the Internet of Things.", Springer, Cham. Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, vol 242., July 2018, . Appendix A. Example CBOR Certificates A.1. Example RFC 7925 profiled X.509 Certificate Example of [RFC7925] profiled X.509 certificate parsed with OpenSSL. Raza, et al. Expires May 28, 2021 [Page 20] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 Certificate: Data: Version: 3 (0x2) Serial Number: 128269 (0x1f50d) Signature Algorithm: ecdsa-with-SHA256 Issuer: CN=RFC test CA Validity Not Before: Jan 1 00:00:00 2020 GMT Not After : Feb 2 00:00:00 2021 GMT Subject: CN=01-23-45-FF-FE-67-89-AB Subject Public Key Info: Public Key Algorithm: id-ecPublicKey Public-Key: (256 bit) pub: 04:ae:4c:db:01:f6:14:de:fc:71:21:28:5f:dc:7f: 5c:6d:1d:42:c9:56:47:f0:61:ba:00:80:df:67:88: 67:84:5e:e9:a6:9f:d4:89:31:49:da:e3:d3:b1:54: 16:d7:53:2c:38:71:52:b8:0b:0d:f3:e1:af:40:8a: 95:d3:07:1e:58 ASN1 OID: prime256v1 NIST CURVE: P-256 X509v3 extensions: X509v3 Key Usage: Digital Signature Signature Algorithm: ecdsa-with-SHA256 30:44:02:20:37:38:73:ef:87:81:b8:82:97:ef:23:5c:1f:ac: cf:62:da:4e:44:74:0d:c2:a2:e6:a3:c6:c8:82:a3:23:8d:9c: 02:20:3a:d9:35:3b:a7:88:68:3b:06:bb:48:fe:ca:16:ea:71: 17:17:34:c6:75:c5:33:2b:2a:f1:cb:73:38:10:a1:fc The DER encoding of the above certificate is 314 bytes. 30 82 01 36 30 81 DE A0 03 02 01 02 02 03 01 F5 0D 30 0A 06 08 2A 86 48 CE 3D 04 03 02 30 16 31 14 30 12 06 03 55 04 03 0C 0B 52 46 43 20 74 65 73 74 20 43 41 30 1E 17 0D 32 30 30 31 30 31 30 30 30 30 30 30 5A 17 0D 32 31 30 32 30 32 30 30 30 30 30 30 5A 30 22 31 20 30 1E 06 03 55 04 03 0C 17 30 31 2D 32 33 2D 34 35 2D 46 46 2D 46 45 2D 36 37 2D 38 39 2D 41 42 30 59 30 13 06 07 2A 86 48 CE 3D 02 01 06 08 2A 86 48 CE 3D 03 01 07 03 42 00 04 AE 4C DB 01 F6 14 DE FC 71 21 28 5F DC 7F 5C 6D 1D 42 C9 56 47 F0 61 BA 00 80 DF 67 88 67 84 5E E9 A6 9F D4 89 31 49 DA E3 D3 B1 54 16 D7 53 2C 38 71 52 B8 0B 0D F3 E1 AF 40 8A 95 D3 07 1E 58 A3 0F 30 0D 30 0B 06 03 55 1D 0F 04 04 03 02 07 80 30 0A 06 08 2A 86 48 CE 3D 04 03 02 03 47 00 30 44 02 20 37 38 73 EF 87 81 B8 82 97 EF 23 5C 1F AC CF 62 DA 4E 44 74 0D C2 A2 E6 A3 C6 C8 82 A3 23 8D 9C 02 20 3A D9 35 3B A7 88 68 3B 06 BB 48 FE CA 16 EA 71 17 17 34 C6 75 C5 33 2B 2A F1 CB 73 38 10 A1 FC Raza, et al. Expires May 28, 2021 [Page 21] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 A.1.1. Example CBOR Certificate Compression The CBOR certificate compression of the X.509 in CBOR diagnostic format is: /This defines a CBOR Sequence (RFC 8742):/ 1, h'01f50d', 6, "RFC test CA", h'2B044180', h'2D543300', h'0123456789AB', 1, h'02ae4cdb01f614defc7121285fdc7f5c6d1d42c95647f061ba 0080df678867845e', 1, h'373873EF8781B88297EF235C1FACCF62DA4E44740DC2A2E6A3 C6C882A3238D9C3AD9353BA788683B06BB48FECA16EA711717 34C675C5332B2AF1CB733810A1FC' The CBOR encoding (CBOR sequence) of the CBOR certificate is 138 bytes. 01 43 01 F5 0D 06 6B 52 46 43 20 74 65 73 74 20 43 41 44 2B 04 41 80 44 2D 54 33 00 46 01 23 45 67 89 AB 01 58 21 02 AE 4C DB 01 F6 14 DE FC 71 21 28 5F DC 7F 5C 6D 1D 42 C9 56 47 F0 61 BA 00 80 DF 67 88 67 84 5E 01 58 40 37 38 73 EF 87 81 B8 82 97 EF 23 5C 1F AC CF 62 DA 4E 44 74 0D C2 A2 E6 A3 C6 C8 82 A3 23 8D 9C 3A D9 35 3B A7 88 68 3B 06 BB 48 FE CA 16 EA 71 17 17 34 C6 75 C5 33 2B 2A F1 CB 73 38 10 A1 FC A.1.2. Example: Natively Signed CBOR Certificate The corresponding natively signed CBOR certificate in CBOR diagnostic format is identical except for type and signatureValue. Raza, et al. Expires May 28, 2021 [Page 22] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 /This defines a CBOR Sequence (RFC 8742):/ 0, h'01f50d', 6, "RFC test CA", h'2B044180', h'2D543300', h'0123456789AB', 1, h'02ae4cdb01f614defc7121285fdc7f5c6d1d42c95647f061 ba0080df678867845e', 1, h'7F10A063DA8DB2FD49414440CDF85070AC22A266C7F1DFB1 577D9A35A295A8742E794258B76968C097F85542322A0796 0199C13CC0220A9BC729EF2ECA638CFE' The CBOR encoding (CBOR sequence) of the CBOR certificate is 138 bytes. 00 43 01 F5 0D 06 6B 52 46 43 20 74 65 73 74 20 43 41 44 2B 04 41 80 44 2D 54 33 00 46 01 23 45 67 89 AB 01 58 21 02 AE 4C DB 01 F6 14 DE FC 71 21 28 5F DC 7F 5C 6D 1D 42 C9 56 47 F0 61 BA 00 80 DF 67 88 67 84 5E 01 58 40 7F 10 A0 63 DA 8D B2 FD 49 41 44 40 CD F8 50 70 AC 22 A2 66 C7 F1 DF B1 57 7D 9A 35 A2 95 A8 74 2E 79 42 58 B7 69 68 C0 97 F8 55 42 32 2A 07 96 01 99 C1 3C C0 22 0A 9B C7 29 EF 2E CA 63 8C FE A.2. Example HTPPS X.509 Certificate The DER encoding of the tools.ietf.org certificate is 1647 bytes. 30 82 06 6b 30 82 05 53 a0 03 02 01 02 02 09 00 a6 a5 5c 87 0e 39 b4 0e 30 0d 06 09 2a 86 48 86 f7 0d 01 01 0b 05 00 30 81 c6 31 0b 30 09 06 03 55 04 06 13 02 55 53 31 10 30 0e 06 03 55 04 08 13 07 41 72 69 7a 6f 6e 61 31 13 30 11 06 03 55 04 07 13 0a 53 63 6f 74 74 73 64 61 6c 65 31 25 30 23 06 03 55 04 0a 13 1c 53 74 61 72 66 69 65 6c 64 20 54 65 63 68 6e 6f 6c 6f 67 69 65 73 2c 20 49 6e 63 2e 31 33 30 31 06 03 55 04 0b 13 2a 68 74 74 70 3a 2f 2f 63 65 72 74 73 2e 73 74 61 72 66 69 65 6c 64 74 65 63 68 2e 63 6f 6d 2f 72 65 70 6f 73 69 74 6f 72 79 2f 31 34 30 32 06 03 Raza, et al. Expires May 28, 2021 [Page 23] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 55 04 03 13 2b 53 74 61 72 66 69 65 6c 64 20 53 65 63 75 72 65 20 43 65 72 74 69 66 69 63 61 74 65 20 41 75 74 68 6f 72 69 74 79 20 2d 20 47 32 30 1e 17 0d 32 30 31 30 30 31 31 39 33 38 33 36 5a 17 0d 32 31 31 31 30 32 31 39 33 38 33 36 5a 30 3e 31 21 30 1f 06 03 55 04 0b 13 18 44 6f 6d 61 69 6e 20 43 6f 6e 74 72 6f 6c 20 56 61 6c 69 64 61 74 65 64 31 19 30 17 06 03 55 04 03 0c 10 2a 2e 74 6f 6f 6c 73 2e 69 65 74 66 2e 6f 72 67 30 82 01 22 30 0d 06 09 2a 86 48 86 f7 0d 01 01 01 05 00 03 82 01 0f 00 30 82 01 0a 02 82 01 01 00 b1 e1 37 e8 eb 82 d6 89 fa db f5 c2 4b 77 f0 2c 4a de 72 6e 3e 13 60 d1 a8 66 1e c4 ad 3d 32 60 e5 f0 99 b5 f4 7a 7a 48 55 21 ee 0e 39 12 f9 ce 0d ca f5 69 61 c7 04 ed 6e 0f 1d 3b 1e 50 88 79 3a 0e 31 41 16 f1 b1 02 64 68 a5 cd f5 4a 0a ca 99 96 35 08 c3 7e 27 5d d0 a9 cf f3 e7 28 af 37 d8 b6 7b dd f3 7e ae 6e 97 7f f7 ca 69 4e cc d0 06 df 5d 27 9b 3b 12 e7 e6 fe 08 6b 52 7b 82 11 7c 72 b3 46 eb c1 e8 78 b8 0f cb e1 eb bd 06 44 58 dc 83 50 b2 a0 62 5b dc 81 b8 36 e3 9e 7c 79 b2 a9 53 8a e0 0b c9 4a 2a 13 39 31 13 bd 2c cf a8 70 cf 8c 8d 3d 01 a3 88 ae 12 00 36 1d 1e 24 2b dd 79 d8 53 01 26 ed 28 4f c9 86 94 83 4e c8 e1 14 2e 85 b3 af d4 6e dd 69 46 af 41 25 0e 7a ad 8b f2 92 ca 79 d9 7b 32 4f f7 77 e8 f9 b4 4f 23 5c d4 5c 03 ae d8 ab 3a ca 13 5f 5d 5d 5d a1 02 03 01 00 01 a3 82 02 e1 30 82 02 dd 30 0c 06 03 55 1d 13 01 01 ff 04 02 30 00 30 1d 06 03 55 1d 25 04 16 30 14 06 08 2b 06 01 05 05 07 03 01 06 08 2b 06 01 05 05 07 03 02 30 0e 06 03 55 1d 0f 01 01 ff 04 04 03 02 05 a0 30 3d 06 03 55 1d 1f 04 36 30 34 30 32 a0 30 a0 2e 86 2c 68 74 74 70 3a 2f 2f 63 72 6c 2e 73 74 61 72 66 69 65 6c 64 74 65 63 68 2e 63 6f 6d 2f 73 66 69 67 32 73 31 2d 32 34 32 2e 63 72 6c 30 63 06 03 55 1d 20 04 5c 30 5a 30 4e 06 0b 60 86 48 01 86 fd 6e 01 07 17 01 30 3f 30 3d 06 08 2b 06 01 05 05 07 02 01 16 31 68 74 74 70 3a 2f 2f 63 65 72 74 69 66 69 63 61 74 65 73 2e 73 74 61 72 66 69 65 6c 64 74 65 63 68 2e 63 6f 6d 2f 72 65 70 6f 73 69 74 6f 72 79 2f 30 08 06 06 67 81 0c 01 02 01 30 81 82 06 08 2b 06 01 05 05 07 01 01 04 76 30 74 30 2a 06 08 2b 06 01 05 05 07 30 01 86 1e 68 74 74 70 3a 2f 2f 6f 63 73 70 2e 73 74 61 72 66 69 65 6c 64 74 65 63 68 2e 63 6f 6d 2f 30 46 06 08 2b 06 01 05 05 07 30 02 86 3a 68 74 74 70 3a 2f 2f 63 65 72 74 69 66 69 63 61 74 65 73 2e 73 74 61 72 66 69 65 6c 64 74 65 63 68 2e 63 6f 6d 2f 72 65 70 6f 73 69 74 6f 72 79 2f 73 66 69 67 32 2e 63 72 74 30 1f 06 03 55 1d 23 04 18 30 16 80 14 25 45 81 68 50 26 38 3d 3b 2d 2c be cd 6a d9 b6 3d b3 66 63 30 2b 06 03 55 1d 11 04 24 30 22 82 10 2a 2e 74 6f 6f 6c 73 2e 69 65 74 66 2e 6f 72 67 82 0e 74 6f 6f 6c 73 2e 69 65 74 66 2e 6f 72 67 30 1d 06 03 55 1d 0e 04 16 04 14 ad 8a b4 1c 07 51 d7 92 89 07 b0 b7 84 62 2f 36 55 7a 5f 4d 30 82 01 06 06 0a 2b 06 01 04 01 d6 79 02 04 02 04 81 f7 04 81 f4 00 f2 00 77 00 f6 5c 94 2f d1 77 30 22 14 54 18 08 30 94 56 8e e3 4d 13 19 33 bf df 0c 2f 20 0b cc 4e f1 64 e3 00 00 01 74 e5 ac 71 13 00 00 04 03 00 48 30 46 02 21 00 8c f5 48 52 ce 56 35 43 39 11 cf 10 cd b9 1f 52 b3 36 39 22 3a d1 38 a4 1d ec a6 fe de 1f e9 0f 02 21 00 bc a2 25 43 66 c1 9a 26 91 c4 7a 00 b5 b6 53 ab bd 44 c2 f8 ba ae f4 d2 da f2 52 7c e6 45 49 95 00 77 00 5c dc 43 92 fe e6 ab 45 44 b1 5e 9a d4 56 e6 10 37 fb d5 fa 47 dc a1 73 94 b2 5e e6 f6 c7 0e ca 00 00 01 74 e5 ac 72 3c 00 00 04 03 00 48 30 46 02 21 00 a5 e0 90 6e 63 e9 1d 4f dd ef ff 03 52 b9 1e 50 89 60 07 56 4b 44 8a 38 28 f5 96 dc 6b 28 72 6d 02 21 00 fc 91 ea ed 02 Raza, et al. Expires May 28, 2021 [Page 24] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 16 88 66 05 4e e1 8a 2e 53 46 c4 cc 51 fe b3 fa 10 a9 1d 2e db f9 91 25 f8 6c e6 30 0d 06 09 2a 86 48 86 f7 0d 01 01 0b 05 00 03 82 01 01 00 14 04 3f a0 be d2 ee 3f a8 6e 3a 1f 78 8e a0 4c 35 53 0f 11 06 1f ff 60 a1 6d 0b 83 e9 d9 2a db b3 3f 9d b3 d7 e0 59 4c 19 a8 e4 19 a5 0c a7 70 72 77 63 d5 fe 64 51 0a d2 7a d6 50 a5 8a 92 38 ec cb 2f 0f 5a c0 64 58 4d 5c 06 b9 73 63 68 27 8b 89 34 dc 79 c7 1d 3a fd 34 5f 83 14 41 58 49 80 68 29 80 39 8a 86 72 69 cc 79 37 ce e3 97 f7 dc f3 95 88 ed 81 03 29 00 d2 a2 c7 ba ab d6 3a 8e ca 09 0b d9 fb 39 26 4b ff 03 d8 8e 2d 3f 6b 21 ca 8a 7d d8 5f fb 94 ba 83 de 9c fc 15 8d 61 fa 67 2d b0 c7 db 3d 25 0a 41 4a 85 d3 7f 49 46 37 3c f4 b1 75 d0 52 f3 dd c7 66 f1 4b fd aa 00 ed bf e4 7e ed 01 ec 7b e4 f6 46 fc 31 fd 72 fe 03 d2 f2 65 af 4d 7e e2 81 9b 7a fd 30 3c f5 52 f4 05 34 a0 8a 3e 19 41 58 c8 a8 e0 51 71 84 09 15 ae ec a5 77 75 fa 18 f7 d5 77 d5 31 cc c7 2d A.2.1. Example CBOR Certificate Compression The CBOR certificate compression of the X.509 in CBOR diagnostic format is: Raza, et al. Expires May 28, 2021 [Page 25] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 /This defines a CBOR Sequence (RFC 8742):/ 1, h'A6A55C870E39B40E', 0, [ [4, "US"], [6, "Arizona"], [5, "Scottsdale"], [7, "Starfield Technologies, Inc."], [8, "http://certs.starfieldtech.com/repository/"], [1, "Starfield Secure Certificate Authority - G2"] ], h'2D3EE7F6', h'2F98B716', [ [8, "Domain Control Validated"], [-1, "*.tools.ietf.org"] ], 0, h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h'30343032a030a02e862c687474703a2f2f63726c2e737461726669656c64746563682e636f6d2f736669673273312d3234322e63726c', 7, h'305A304E060B6086480186FD6E01071701303F303D06082B060105050702011631687474703A2F2F6365727469666963617465732E737461726669656C64746563682E636F6D2F7265706F7369746F72792F3008060667810C010201', 9, h'3074302A06082B06010505073001861E687474703A2F2F6F6373702E737461726669656C64746563682E636F6D2F304606082B06010505073002863A687474703A2F2F6365727469666963617465732E737461726669656C64746563682E636F6D2F7265706F7369746F72792F73666967322E637274', 5, h'30168014254581685026383D3B2D2CBECD6AD9B63DB36663', 4, [ 2, "*.tools.ietf.org", 2, "tools.ietf.org" ], 6, h'0414AD8AB41C0751D7928907B0B784622F36557A5F4D', 10, h'0481F400F2007700F65C942FD1773022145418083094568EE34D131933BFDF0C2F200BCC4EF164E300000174E5AC711300000403004830460221008CF54852CE5635433911CF10CDB91F52B33639223AD138A41DECA6FEDE1FE90F022100BCA2254366C19A2691C47A00B5B653ABBD44C2F8BAAEF4D2DAF2527CE64549950077005CDC4392FEE6AB4544B15E9AD456E61037FBD5FA47DCA17394B25EE6F6C70ECA00000174E5AC723C0000040300483046022100A5E0906E63E91D4FDDEFFF0352B91E50896007564B448A3828F596DC6B28726D022100FC91EAED02168866054EE18A2E5346C4CC51FEB3FA10A91D2EDBF99125F86CE6' ], h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he CBOR encoding (CBOR sequence) of the CBOR certificate is 1374 bytes. Appendix B. X.509 Certificate Profile, ASN.1 EDITOR'S NOTE: The ASN.1 below is not up to date with the rest of the specification. The below ASN.1 for RFC 7925 profile should be in draft-ietf-uta-tls13-iot-profile instead. If CBOR Certificates support a large subset of RFC 5280, we should probably not duplicate all the ASN.1 in that document. Should be discussed what kind and how much (if any) ASN.1 this document needs. If possible, one option would be to have ASN.1 for the restrictions compared to RFC 5280. Raza, et al. Expires May 28, 2021 [Page 26] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 IOTCertificate DEFINITIONS EXPLICIT TAGS ::= BEGIN Certificate ::= SEQUENCE { tbsCertificate TBSCertificate, signatureAlgorithm AlgorithmIdentifier, signatureValue BIT STRING } TBSCertificate ::= SEQUENCE { version [0] INTEGER {v3(2)}, serialNumber INTEGER (1..MAX), signature AlgorithmIdentifier, issuer Name, validity Validity, subject Name, subjectPublicKeyInfo SubjectPublicKeyInfo, extensions [3] Extensions OPTIONAL } Name ::= SEQUENCE SIZE (1) OF DistinguishedName DistinguishedName ::= SET SIZE (1) OF CommonName CommonName ::= SEQUENCE { type OBJECT IDENTIFIER (id-at-commonName), value UTF8String } Validity ::= SEQUENCE { notBefore UTCTime, notAfter UTCTime } SubjectPublicKeyInfo ::= SEQUENCE { algorithm AlgorithmIdentifier, subjectPublicKey BIT STRING } AlgorithmIdentifier ::= SEQUENCE { algorithm OBJECT IDENTIFIER, parameters ANY DEFINED BY algorithm OPTIONAL } } Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension Extension ::= SEQUENCE { extnId OBJECT IDENTIFIER, critical BOOLEAN DEFAULT FALSE, Raza, et al. Expires May 28, 2021 [Page 27] Internet-DraftCBOR Encoding of X.509 Certificates (CBOR CerNovember 2020 extnValue OCTET STRING } id-at-commonName OBJECT IDENTIFIER ::= {joint-iso-itu-t(2) ds(5) attributeType(4) 3} END Acknowledgments The authors want to thank Henk Birkholz, Carsten Bormann, Russ Housley, Olle Johansson, Benjamin Kaduk, Ilari Liusvaara, Laurence Lundblade, Thomas Peterson, Michael Richardson, Stefan Santesson, Jim Schaad, Fraser Tweedale, and Rene Struik for reviewing and commenting on intermediate versions of the draft. Authors' Addresses Shahid Raza RISE AB Email: shahid.raza@ri.se Joel Hoeglund RISE AB Email: joel.hoglund@ri.se Goeran Selander Ericsson AB Email: goran.selander@ericsson.com John Preuss Mattsson Ericsson AB Email: john.mattsson@ericsson.com Martin Furuhed Nexus Group Email: martin.furuhed@nexusgroup.com Raza, et al. Expires May 28, 2021 [Page 28]