| Internet-Draft | CBOR Encoding of X.509 Certificates (CBO | December 2020 |
| Raza, et al. | Expires 4 June 2021 | [Page] |
This document specifies a CBOR encoding of 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 significantly reduces the size of certificates compatible with RFC 7925 and IEEE 802.1AR (DevIDs). When used to re-encode DER encoded X.509 certificates, the CBOR encoding can in many cases reduce the size of RFC 7925 profiled certificates with over 50%. The CBOR encoding can also be used encode "natively signed" CBOR certificates, which does not require re-encoding for the signature to be verified. The document also specifies COSE headers as well as a TLS certificate type for CBOR certificates.¶
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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.¶
One of the challenges with deploying a Public Key Infrastructure (PKI) for the Internet of Things (IoT) is the size and parsing 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] and IEEE 802.1AR [IEEE-802.1AR] specify certificate profiles for Internet of Things deployments which can be applied to lightweight certificate based authentication with, e.g., TLS [RFC8446], DTLS [I-D.ietf-tls-dtls13], COSE [RFC8152], EDHOC [I-D.ietf-lake-edhoc] or Compact TLS 1.3 [I-D.ietf-tls-ctls]. This document specifies a CBOR encoding based on [X.509-IoT], which can support large parts of [RFC5280]. The encoding support all [RFC7925] and IEEE 802.1AR [IEEE-802.1AR] profiled X.509 certificates. Two variants are defined using the same CBOR encoding and differing only in what is being signed:¶
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.¶
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].¶
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] and [IEEE-802.1AR]. In the CBOR encoding, static fields are elided, elliptic curve points and time values are compressed, OID are replaced with short integers, 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 2.¶
The CBOR certificate can be either a CBOR re-encoding of a DER encoded 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]. The re-encoding is known to work with DER encoded certificates but might work with other canonical encodings. The re-encoding 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.¶
The X.509 fields and their CBOR encodings are listed below, and used in the definition of CBOR Certificates, see Figure 1.¶
CBOR certificates are defined in terms of DER encoded [RFC5280] X.509 certificates:¶
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.¶
; The elements of the following array are to be used in a CBOR Sequence: CBORCertificate = [ TBSCertificate, issuerSignatureValue : bytes, ] TBSCertificate = ( cborCertificateType : int, certificateSerialNumber : CertificateSerialNumber, issuer : Name, validityNotBefore : Time, validityNotAfter : Time / null, subject : Name, subjectPublicKeyAlgorithm : Algorithm, subjectPublicKey : bytes, extensions : Extensions, issuerSignatureAlgorithm : Algorithm, ) CertificateSerialNumber = ~biguint Name = [ * [ + Attribute ] ] / text / bytes Attribute = ( attributeType : int, attributeValue : text ) Time = ~time Algorithm = int / oid Extensions = [ * Extension ] / int Extension = ( extensionID : int / oid, ? critical : bool, ; present if and only if extensionID is an oid extensionValue : any, ; type known from extensionID )
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?¶
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] and [IEEE-802.1AR] are encoded as follows:¶
ExtValueEKU = [ + int / oid ] / int¶
GeneralNames = [ + GeneralName ] / text GeneralName = ( GeneralNameType : int, GeneralNameValue : any )¶
KeyIdentifier = bytes¶
ExtValueAIA = [ + ( ocsp : 1 // caIssuers : 2 , uri : text ) ]¶
The examples below use values from Section 9.3, Section 9.4, and Section 9.5:¶
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" ].¶
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¶
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 likely to be 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.¶
The CBOR encoding of the sample certificate given in Appendix A results in the numbers shown in Figure 2. 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 | +------------------+--------------+------------+--------------------+
The difference between CBOR encoded 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 encodings which reduces the processing in the authenticating devices, and avoids known complexities and security issues with these encodings.¶
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 encoded X.509 certificates provides an intermediate step between [RFC7925] or [IEEE-802.1AR] profiled X.509 certificates and natively signed CBOR certificates: An implementation of CBOR encoded 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 also other benefits. For example, 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.¶
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.¶
The use of natively signed CBOR certificates removes the need for ASN.1 encoding, which is a rich source of security vulnerabilities.¶
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.¶
This document creates several new registries under the new heading "CBOR Certificate". For all items, the 'Reference' field points to this document.¶
The expert reviewers for the registries defined in this document are expected to ensure that the usage solves a valid use case that could not be solved better in a different way, that it is not going to duplicate one that is already registered, and that the registered point is likely to be used in deployments. They are furthermore expected to check the clarity of purpose and use of the requested code points. Experts should take into account the expected usage of entries when approving point assignment, and the length of the encoded value should be weighed against the number of code points left that encode to that size and the size of device it will be used on. Values in the interval [-24, 23] have a 1 byte encodings, other values in the interval [-256, 255] have a 2 byte encodings, and the remaning values in the interval [-65536, 65535] have 3 byte encodings.¶
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" and "Expert 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 following X.509 v3 | | 1 | CBOR re-encoding of X.509 v3 Certificate | +-------+-----------------------------------------------------+
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 non-negative values can be registered. For values in the interval [0, 23] the registration procedure is "IETF Review" and "Expert Review". For all other values the registration procedure is "Expert Review". The initial contents of the registry are:¶
+-------+---------------------------------------+ | Value | X.509 Attribute Type | +=======+=======================================+ | 0 | id-emailAddress | | 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 | +-------+---------------------------------------+
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" and "Expert Review". For all other values the registration procedure is "Expert Review". The initial contents of the registry are:¶
+-------+-------------------------------------+------------------+ | Value | X.509 Extension Type | extensionValue | +=======+=====================================+==================+ | 1 | id-ce-basicConstraints | int | | 2 | id-ce-keyUsage | int | | 3 | id-ce-extKeyUsage | ExtValueEKU | | 4 | id-ce-subjectAltName | GeneralNames | | 5 | id-ce-authorityKeyIdentifier | ExtValueAKI | | 6 | id-ce-subjectKeyIdentifier | KeyIdentifier | | 7 | id-ce-certificatePolicies | bytes | | 8 | id-ce-cRLDistributionPoints | GeneralNames | | 9 | id-pe-authorityInfoAccess | ExtValueAIA | | 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-policyMappings | bytes | | 252 | id-ce-issuerAltName | GeneralNames | | 253 | id-ce-subjectDirectoryAttributes | bytes | | 254 | id-ce-freshestCRL | bytes | | 255 | id-pe-subjectInfoAccess | bytes | +-------+-------------------------------------+------------------+
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" and "Expert Review". For all other values the registration procedure is "Expert Review". The initial contents of the registry are:¶
+-------+---------------------------------------+ | 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 | +-------+---------------------------------------+
IANA has created a new registry titled "CBOR General Name Registry" under the new heading "CBOR Certificate". The columns of the registry are Value, General Name, 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" and "Expert Review". For all other values the registration procedure is "Expert Review". The initial contents of the registry are:¶
+-------+-----------------------------------+------------------+ | Value | General Name Type | Value | +=======+===================================+==================+ | -1 | otherName + hardwareModuleName | [ oid, bytes ] | | 0 | otherName | [ oid, bytes ] | | 1 | rfc822Name | text | | 2 | dNSName | text | | 4 | directoryName | Name | | 6 | uniformResourceIdentifier | text | | 7 | iPAddress | bytes | | 8 | registeredID | oid | +-------+-----------------------------------+------------------+
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" and "Expert 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:¶
+-------+---------------------------------------+ | Value | X.509 Signature Algorithm | +=======+=======================================+ | -256 | sha1WithRSAEncryption | | -255 | ecdsa-with-SHA1 | | 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 | | 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 | +-------+---------------------------------------+
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" and "Expert 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:¶
+-------+---------------------------------------+ | 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 | +-------+---------------------------------------+
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 | +-----------+-------+----------------+---------------------+¶
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 | | +-------+------------------+-------------+---------+¶
Example of [RFC7925] profiled X.509 certificate parsed with OpenSSL.¶
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:b1:21:6a:b9:6e:5b:3b:33:40:f5:bd:f0:2e:69:
3f:16:21:3a:04:52:5e:d4:44:50:b1:01:9c:2d:fd:
38:38:ab:ac:4e:14:d8:6c:09:83:ed:5e:9e:ef:24:
48:c6:86:1c:c4:06:54:71:77:e6:02:60:30:d0:51:
f7:79:2a:c2:06
ASN1 OID: prime256v1
NIST CURVE: P-256
X509v3 extensions:
X509v3 Key Usage:
Digital Signature
Signature Algorithm: ecdsa-with-SHA256
30:44:02:20:44:5d:79:8c:90:e7:f5:00:dc:74:7a:65:4c:ec:
6c:fa:6f:03:72:76:e1:4e:52:ed:07:fc:16:29:4c:84:66:0d:
02:20:5a:33:98:5d:fb:d4:bf:dd:6d:4a:cf:38:04:c3:d4:6e:
bf:3b:7f:a6:26:40:67:4f:c0:35:4f:a0:56:db:ae:a6
¶
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 B1 21 6A B9 6E 5B 3B 33 40 F5 BD F0 2E 69 3F 16 21 3A 04 52 5E D4 44 50 B1 01 9C 2D FD 38 38 AB AC 4E 14 D8 6C 09 83 ED 5E 9E EF 24 48 C6 86 1C C4 06 54 71 77 E6 02 60 30 D0 51 F7 79 2A C2 06 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 44 5D 79 8C 90 E7 F5 00 DC 74 7A 65 4C EC 6C FA 6F 03 72 76 E1 4E 52 ED 07 FC 16 29 4C 84 66 0D 02 20 5A 33 98 5D FB D4 BF DD 6D 4A CF 38 04 C3 D4 6E BF 3B 7F A6 26 40 67 4F C0 35 4F A0 56 DB AE A6¶
The CBOR encoding of the same X.509 certificate is shown below in CBOR diagnostic format.¶
/This defines a CBOR Sequence (RFC 8742):/
1,
h'01f50d',
"RFC test CA",
1577836800,
1612224000,
h'0123456789AB',
1,
h'02B1216AB96E5B3B3340F5BDF02E693F16213A04525ED44450
B1019C2DFD3838AB',
1,
6,
h'445D798C90E7F500DC747A654CEC6CFA6F037276E14E52ED07
FC16294C84660D5A33985DFBD4BFDD6D4ACF3804C3D46EBF3B
7FA62640674FC0354FA056DBAEA6
¶
The size of the CBOR encoding (CBOR sequence) is 138 bytes.¶
01 43 01 F5 0D 6B 52 46 43 20 74 65 73 74 20 43 41 1A 5E 0B E1 00 1A 60 18 96 00 46 01 23 45 67 89 AB 01 58 21 02 B1 21 6A B9 6E 5B 3B 33 40 F5 BD F0 2E 69 3F 16 21 3A 04 52 5E D4 44 50 B1 01 9C 2D FD 38 38 AB 01 06 58 40 44 5D 79 8C 90 E7 F5 00 DC 74 7A 65 4C EC 6C FA 6F 03 72 76 E1 4E 52 ED 07 FC 16 29 4C 84 66 0D 5A 33 98 5D FB D4 BF DD 6D 4A CF 38 04 C3 D4 6E BF 3B 7F A6 26 40 67 4F C0 35 4F A0 56 DB AE A6¶
The corresponding natively signed CBOR certificate in CBOR diagnostic format is identical, except for cborCertificateType and signatureValue.¶
/This defines a CBOR Sequence (RFC 8742):/
0,
h'01f50d',
"RFC test CA",
1577836800,
1612224000,
h'0123456789AB',
1,
h'02B1216AB96E5B3B3340F5BDF02E693F16213A04525ED44450
B1019C2DFD3838AB',
1,
6,
h'B27A0B781455F71B68290F6C2EC9A897F18FDE9B6C59575953
BC67268AB0E4DDE99D273E04E4715383AB2257C6AAA35284E5
ED18BDB91247E9F2C433136480B9'
¶
The size of the CBOR encoding (CBOR sequence) is 138 bytes.¶
00 43 01 F5 0D 6B 52 46 43 20 74 65 73 74 20 43 41 1A 5E 0B E1 00 1A 60 18 96 00 46 01 23 45 67 89 AB 01 58 21 02 B1 21 6A B9 6E 5B 3B 33 40 F5 BD F0 2E 69 3F 16 21 3A 04 52 5E D4 44 50 B1 01 9C 2D FD 38 38 AB 01 06 58 40 B2 7A 0B 78 14 55 F7 1B 68 29 0F 6C 2E C9 A8 97 F1 8F DE 9B 6C 59 57 59 53 BC 67 26 8A B0 E4 DD E9 9D 27 3E 04 E4 71 53 83 AB 22 57 C6 AA A3 52 84 E5 ED 18 BD B9 12 47 E9 F2 C4 33 13 64 80 B9¶
All of the the above example certificate were signed and can be verified with the following key pair where the private key is encoded as in COSE [RFC8152].¶
issuerPublicKeyAlgorithm : 1 (id-ecPublicKey + secp256r1) issuerPublicKey : h'02AE4CDB01F614DEFC7121285FDC7F5C6D1D42C95647F061BA0080DF678867845E' issuerPrivateKey : h'DC66B3415456D649429B53223DF7532B942D6B0E0842C30BCA4C0ACF91547BB2'¶
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 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 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¶
The CBOR encoding of the X.509 certificate is shown below in CBOR diagnostic format.¶
/This defines a CBOR Sequence (RFC 8742):/
1,
h'A6A55C870E39B40E',
[
[-4, "US"],
[-6, "Arizona"],
[-5, "Scottsdale"],
[-7, "Starfield Technologies, Inc."],
[-8, "http://certs.starfieldtech.com/repository/"],
[-1, "Starfield Secure Certificate Authority - G2"]
],
1601581116,
1635881916,
[
[-8, "Domain Control Validated"],
[1, "*.tools.ietf.org"]
],
0,
h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
[
-1, -2,
3, [ 1, 2 ],
-2, 5,
8, "http://crl.starfieldtech.com/sfig2s1-242.crl",
7, h'305A304E060B6086480186FD6E01071701303F303D06082B060105050702011631687474703A2F2F6365727469666963617465732E737461726669656C64746563682E636F6D2F7265706F7369746F72792F3008060667810C010201',
9, [ 1, "http://ocsp.starfieldtech.com/", 2, "http://certificates.starfieldtech.com/repository/sfig2.crt" ],
5, h'254581685026383D3B2D2CBECD6AD9B63DB36663',
4, [ 2, "*.tools.ietf.org", 2, "tools.ietf.org" ],
6, h'AD8AB41C0751D7928907B0B784622F36557A5F4D',
10, h'0481F400F2007700F65C942FD1773022145418083094568EE34D131933BFDF0C2F200BCC4EF164E300000174E5AC711300000403004830460221008CF54852CE5635433911CF10CDB91F52B33639223AD138A41DECA6FEDE1FE90F022100BCA2254366C19A2691C47A00B5B653ABBD44C2F8BAAEF4D2DAF2527CE64549950077005CDC4392FEE6AB4544B15E9AD456E61037FBD5FA47DCA17394B25EE6F6C70ECA00000174E5AC723C0000040300483046022100A5E0906E63E91D4FDDEFFF0352B91E50896007564B448A3828F596DC6B28726D022100FC91EAED02168866054EE18A2E5346C4CC51FEB3FA10A91D2EDBF99125F86CE6'
],
1,
h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
¶
The size of the CBOR encoding (CBOR sequence) is 1332 bytes.¶
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.¶
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,
extnValue OCTET STRING
}
id-at-commonName OBJECT IDENTIFIER ::=
{joint-iso-itu-t(2) ds(5) attributeType(4) 3}
END
¶
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.¶