| Internet-Draft | TST Header | January 2025 |
| Birkholz, et al. | Expires 26 July 2025 | [Page] |
This document defines two CBOR Signing And Encrypted (COSE) header parameters for incorporating RFC 3161-based timestamping into COSE message structures (COSE_Sign and COSE_Sign1).
This enables the use of established RFC 3161 timestamping infrastructure to prove the creation time of a message.¶
This note is to be removed before publishing as an RFC.¶
Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-cose-tsa-tst-header-parameter/.¶
Source for this draft and an issue tracker can be found at https://github.com/ietf-scitt/draft-birkholz-cose-tsa-tst-header-parameter.¶
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 26 July 2025.¶
Copyright (c) 2025 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
RFC 3161 [RFC3161] provides a method to timestamp a message digest to prove that it was created before a given time.¶
This document defines two new CBOR Object Signing and Encryption (COSE) [STD96] header parameters that carry the TimestampToken (TST) output of RFC 3161, thus allowing existing and widely deployed trust infrastructure to be used with COSE structures used for signing (COSE_Sign and COSE_Sign1).¶
This section discusses two use cases, each representing one of the two modes of use defined in Section 2.¶
A first use case is a digital document signed alongside a trustworthy timestamp. This is a common case in legal contracts. In such scenario, the document signer wants to reinforce the claim that the document existed on a specific date. To achieve this, the document signer acquires a fresh TST for the document from a TSA, combines it with the document, and then signs the bundle. Later on, a relying party consuming the signed bundle can be certain that the document existed at least at the time specified by the TSA. The relying party does not have to trust the signer's clock, which may have been maliciously altered or simply inaccurate.¶
This usage scenario motivates the "Timestamp then COSE" mode defined in Section 2.1.¶
A second use case is the notarization of a signed document by registering it at a Transparency Service. This is common for accountability and auditability of issued documents. Once a document is registered at a Transparency Service's append-only log, its log entry cannot be changed. In certain cases, such as when a short-lived certificate is used for the signature, the registration policy of a Transparency Service may add a trustworthy timestamp to the signed document. This is done to lock the signature to a specific point in time. To achieve this, the Transparency Service acquires a TST from a TSA, bundles it alongside the signed document, and then registers it. A relying party that wants to ascertain the authenticity of the document after the signing key has expired (or has been compromised), can do so by making sure that no revocation information has been made public before the time asserted in the TST.¶
This usage scenario motivates the "COSE then Timestamp" mode described in Section 2.2.¶
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.¶
There are two different modes of composing COSE protection and timestamping, motivated by the usage scenarios discussed above.¶
The diagrams in this section illustrate the processing flow of the specified modes.
For simplicity, only the COSE_Sign1 processing is shown.
Similar diagrams for COSE_Sign can be derived by allowing multiple private-key boxes and replacing the label [signature] with [signatures].¶
Figure 1 shows the case where a datum is first digested and submitted to a TSA to be timestamped.¶
This mode is utilized when the signature should also be performed over the timestamp to provide an immutable timestamp.¶
A signed COSE message is then built as follows:¶
Figure 2 shows the case where the signature(s) field of the signed COSE object is digested and submitted to a TSA to be timestamped. The obtained timestamp token is then added back as an unprotected header into the same COSE object.¶
This mode is utilized when a record of the timing of the signature operation is desired.¶
In this context, timestamp tokens are similar to a countersignature made by the TSA.¶
The two modes described in Section 2.1 and Section 2.2 use different inputs into the timestamping machinery, and consequently create different kinds of binding between COSE and TST. To clearly separate their semantics two different COSE header parameters are defined as described in the following subsections.¶
3161-ttc
The 3161-ttc COSE protected header parameter MUST be used for the mode described in Section 2.1.¶
The 3161-ttc protected header parameter contains a DER-encoded RFC3161 TimeStampToken wrapped in a CBOR byte string (Major type 2).¶
The MessageImprint sent to the TSA (Section 2.4 of [RFC3161]) MUST be the hash of the payload of the COSE signed object.
This does not include the bstr-wrapping, only the payload bytes.¶
To minimize dependencies, the hash algorithm used for signing the COSE message SHOULD be the same as the algorithm used in the RFC3161 MessageImprint.¶
3161-ctt
The 3161-ctt COSE unprotected header parameter MUST be used for the mode described in Section 2.2.¶
The 3161-ctt unprotected header parameter contains a DER-encoded RFC3161 TimeStampToken wrapped in a CBOR byte string (Major type 2).¶
The MessageImprint sent in the request to the TSA MUST be:¶
the hash of the CBOR-encoded signature field of the COSE_Sign1 message, or¶
the hash of the CBOR-encoded signatures field of the COSE_Sign message.¶
In either case, to minimize dependencies, the hash algorithm SHOULD be the same as the algorithm used for signing the COSE message. This may not be possible if the timestamp token has been obtained outside the processing context in which the COSE object is assembled.¶
Refer to Section 3.2.1 and Section 3.2.2 for concrete examples of MessageImprint computation.¶
MessageImprint Computation for COSE_Sign1
Using as an example the COSE_Sign1 message¶
18(
[
/ protected h'a10126' / << {
/ alg / 1:-7 / ECDSA 256 /
} >>,
/ unprotected / {
/ kid / 4:'11'
},
/ payload / 'This is the content.',
/ signature / h'8eb33e4ca31d1c465ab05aac34cc6b23d58fef5c083106c4
d25a91aef0b0117e2af9a291aa32e14ab834dc56ed2a223444547e01f11d3b0916e5
a4c345cacb36'
]
)
¶
then the bstr-wrapped signature¶
58 40 # bytes(64) 8eb33e4ca31d1c465ab05aac34cc6b23 d58fef5c083106c4d25a91aef0b0117e 2af9a291aa32e14ab834dc56ed2a2234 44547e01f11d3b0916e5a4c345cacb36¶
(including the heading bytes 0x5840) is used as input for computing the MessageImprint.¶
When using SHA-256, the resulting MessageImprint is¶
SEQUENCE {
SEQUENCE {
OBJECT IDENTIFIER sha-256 (2 16 840 1 101 3 4 2 1)
NULL
}
OCTET STRING
44 C2 41 9D 13 1D 53 D5 55 84 B5 DD 33 B7 88 C2
4E 55 1C 6D 44 B1 AF C8 B2 B8 5E 69 54 76 3B 4E
}
¶
MessageImprint Computation for COSE_Sign
Using as an example the COSE_Sign message¶
98(
[
/ protected / h'',
/ unprotected / {},
/ payload / 'This is the content.',
/ signatures / [
[
/ protected h'a10126' / << {
/ alg / 1:-7 / ECDSA 256 /
} >>,
/ unprotected / {
/ kid / 4:'11'
},
/ signature / h'e2aeafd40d69d19dfe6e52077c5d7ff4e408282cbefb
5d06cbf414af2e19d982ac45ac98b8544c908b4507de1e90b717c3d34816fe926a2b
98f53afd2fa0f30a'
]
]
]
)
¶
then the signatures array¶
81 # array(1)
83 # array(3)
43 # bytes(3)
a10126
a1 # map(1)
04 # unsigned(4)
42 # bytes(2)
3131 # "11"
58 40 # bytes(64)
e2aeafd40d69d19dfe6e52077c5d7ff4
e408282cbefb5d06cbf414af2e19d982
ac45ac98b8544c908b4507de1e90b717
c3d34816fe926a2b98f53afd2fa0f30a
¶
is used as input for computing the MessageImprint.¶
When using SHA-256, the resulting MessageImprint is¶
SEQUENCE {
SEQUENCE {
OBJECT IDENTIFIER sha-256 (2 16 840 1 101 3 4 2 1)
NULL
}
OCTET STRING
80 3F AD A2 91 2D 6B 7A 83 3A 27 BD 96 1C C0 5B
C1 CC 16 47 59 B1 C5 6F 7A A7 71 E4 E2 15 26 F7
}
¶
RFC 3161 timestamp tokens use CMS as signature envelope format. [STD70] provides the details about signature verification, and [RFC3161] provides the details specific to timestamp token validation. The payload of the signed timestamp token is the TSTInfo structure defined in [RFC3161], which contains the MessageImprint that was sent to the TSA. The hash algorithm is contained in the MessageImprint structure, together with the hash itself.¶
As part of the signature verification, the receiver MUST make sure that the MessageImprint in the embedded timestamp token matches a hash of either the payload, signature, or signature fields, depending on the mode of use and type of COSE structure.¶
Appendix B of [RFC3161] provides an example that illustrates how timestamp tokens can be used to verify signatures of a timestamped message when utilizing X.509 certificates.¶
Please review the Security Considerations section in [RFC3161]; these considerations apply to this document as well.¶
Also review the Security Considerations section in [STD96]; these considerations apply to this document as well, especially the need for implementations to protect private key material.¶
The following scenario assumes an attacker can manipulate the clocks on the COSE signer and its relying parties, but not the TSA. It is also assumed that the TSA is a trusted third party, so the attacker cannot impersonate the TSA and create valid timestamp tokens. In such a setting, any tampering with the COSE signer's clock does not have an impact because, once the timestamp is obtained from the TSA, it becomes the only reliable source of time. However, in both CTT and TTC mode, a denial of service can occur if the attacker can adjust the relying party's clock so that the CMS validation fails. This could disrupt the timestamp validation.¶
In CTT mode, an attacker could manipulate the unprotected header by removing or replacing the timestamp. To avoid that, the signed COSE object should be integrity protected during transit and at rest.¶
In TTC mode, the TSA is given an opaque identifier (a cryptographic hash value) for the payload. While this means that the content of the payload is not directly revealed, to prevent comparison with known payloads or disclosure of identical payloads being used over time, the payload would need to be armored, e.g., with a nonce that is shared with the recipient of the header parameter but not the TSA. Such a mechanism can be employed inside the ones described in this specification, but is out of scope for this document.¶
IANA is requested to add the COSE header parameters defined in Table 1 to the "COSE Header Parameters" registry [IANA.cose_header-parameters].¶
| Name | Label | Value Type | Value Registry | Description | Reference |
|---|---|---|---|---|---|
3161-ttc
|
TBD1 | bstr | - | RFC 3161 timestamp token: Timestamp then COSE | RFCthis, Section 3.1 |
3161-ctt
|
TBD2 | bstr | - | RFC 3161 timestamp token: COSE then Timestamp | RFCthis, Section 3.2 |
The payload¶
This is the content.¶
is hashed using SHA-256 to create the TimeStampReq object¶
SEQUENCE {
INTEGER 1
SEQUENCE {
SEQUENCE {
OBJECT IDENTIFIER sha-256 (2 16 840 1 101 3 4 2 1)
NULL
}
OCTET STRING
09 E6 38 D4 AA 95 FD 72 71 86 62 03 59 53 03 BC
E2 32 F4 62 A9 4D 38 E3 93 77 3C D3 AA E3 F6 B0
}
BOOLEAN TRUE
}
¶
which is sent to the Time Stamping Authority.¶
A TimeStampResp is returned which contains the TimeStampToken¶
SEQUENCE {
OBJECT IDENTIFIER signedData (1 2 840 113549 1 7 2)
[0] {
SEQUENCE {
INTEGER 3
SET {
SEQUENCE {
OBJECT IDENTIFIER sha-512 (2 16 840 1 101 3 4 2 3)
NULL
}
}
SEQUENCE {
OBJECT IDENTIFIER tSTInfo (1 2 840 113549 1 9 16 1 4)
[0] {
OCTET STRING, encapsulates {
SEQUENCE {
INTEGER 1
OBJECT IDENTIFIER '1 2 3 4 1'
SEQUENCE {
SEQUENCE {
OBJECT IDENTIFIER sha-256 (2 16 840 1 101 3 4 2 1)
NULL
}
OCTET STRING
09 E6 38 D4 AA 95 FD 72 71 86 62 03 59 53 03 BC
E2 32 F4 62 A9 4D 38 E3 93 77 3C D3 AA E3 F6 B0
}
INTEGER 85048992
GeneralizedTime 18/01/2025 11:20:06 GMT
BOOLEAN TRUE
[...]
¶
The contents of the TimeStampToken are bstr-wrapped and added to the protected headers bucket which is then signed alongside the original payload to obtain the COSE_Sign1 object¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
18([
<<{1: -7, 258: h'\
3082154906092a864886f70d010702a082153a30821536020103310f300d06096086\
48016503040203050030820184060b2a864886f70d0109100104a08201730482016f\
3082016b02010106042a0304013031300d06096086480165030402010500042009e6\
38d4aa95fd7271866203595303bce232f462a94d38e393773cd3aae3f6b002040511\
bea0180f32303235303131383131323030365a0101ffa0820111a482010d30820109\
3111300f060355040a13084672656520545341310c300a060355040b130354534131\
763074060355040d136d54686973206365727469666963617465206469676974616c\
6c79207369676e7320646f63756d656e747320616e642074696d65207374616d7020\
7265717565737473206d616465207573696e672074686520667265657473612e6f72\
67206f6e6c696e65207365727669636573311830160603550403130f7777772e6672\
65657473612e6f72673122302006092a864886f70d0109011613627573696c657a61\
7340676d61696c2e636f6d3112301006035504071309577565727a62757267310b30\
09060355040613024445310f300d0603550408130642617965726ea0821008308208\
01308205e9a003020102020900c1e986160da8e982300d06092a864886f70d01010d\
05003081953111300f060355040a130846726565205453413110300e060355040b13\
07526f6f74204341311830160603550403130f7777772e667265657473612e6f7267\
3122302006092a864886f70d0109011613627573696c657a617340676d61696c2e63\
6f6d3112301006035504071309577565727a62757267310f300d0603550408130642\
617965726e310b3009060355040613024445301e170d313630333133303135373339\
5a170d3236303331313031353733395a308201093111300f060355040a1308467265\
6520545341310c300a060355040b130354534131763074060355040d136d54686973\
206365727469666963617465206469676974616c6c79207369676e7320646f63756d\
656e747320616e642074696d65207374616d70207265717565737473206d61646520\
7573696e672074686520667265657473612e6f7267206f6e6c696e65207365727669\
636573311830160603550403130f7777772e667265657473612e6f72673122302006\
092a864886f70d0109011613627573696c657a617340676d61696c2e636f6d311230\
1006035504071309577565727a62757267310b3009060355040613024445310f300d\
0603550408130642617965726e30820222300d06092a864886f70d01010105000382\
020f003082020a0282020100b591048c4e486f34e9dc08627fc2375162236984b82c\
b130beff517cfc38f84bce5c65a874dab2621ae0bce7e33563e0ede934fd5f882315\
9f07848808227460c1ed88261706f4281334359dfbb81bd1353fc179610af1a8c8c8\
65dc00ea23b3a89be6bd03ba85a9ec827d60565905e22d6a584ed1380ae150280cee\
397e98a012f380464007862443bc077cb95f421af31712d9683cdb6dffbaf3c8ba5b\
a566ae523d459d6177346d4d840e27886b7c01c5b890d78a2e27bba8dd2f9a2812e1\
57d62f921c65962548069dcdb7d06de181de0e9570d66f87220ce28b628ab55906f3\
ee0c210f7051e8f4858af8b9a92d09e46af2d9cba5bfcfad168cdf604491a4b06603\
b114caf7031f065e7eeefa53c575f3490c059d2e32ddc76ac4d4c4c710683b97fd1b\
e591bc61055186d88f9a0391b307b6f91ed954daa36f9acd6a1e14aa2e4adf17464b\
54db18dbb6ffe30080246547370436ce4e77bae5de6fe0f3f9d6e7ffbeb461e794e9\
2fb0951f8aae61a412cce9b21074635c8be327ae1a0f6b4a646eb0f8463bc63bf845\
530435d19e802511ec9f66c3496952d8becb69b0aa4d4c41f60515fe7dcbb89319cd\
da59ba6aea4be3ceae718e6fcb6ccd7db9fc50bb15b12f3665b0aa307289c2e6dd4b\
111ce48ba2d9efdb5a6b9a506069334fb34f6fc7ae330f0b34208aac80df3266fdd9\
0465876ba2cb898d9505315b6e7b0203010001a38201db308201d730090603551d13\
04023000301d0603551d0e041604146e760b7b4e4f9ce160ca6d2ce927a2a294b377\
37301f0603551d23041830168014fa550d8c346651434cf7e7b3a76c95af7ae6a497\
300b0603551d0f0404030206c030160603551d250101ff040c300a06082b06010505\
070308306306082b0601050507010104573055302a06082b06010505073002861e68\
7474703a2f2f7777772e667265657473612e6f72672f7473612e637274302706082b\
06010505073001861b687474703a2f2f7777772e667265657473612e6f72673a3235\
363030370603551d1f0430302e302ca02aa0288626687474703a2f2f7777772e6672\
65657473612e6f72672f63726c2f726f6f745f63612e63726c3081c60603551d2004\
81be3081bb3081b80601003081b2303306082b060105050702011627687474703a2f\
2f7777772e667265657473612e6f72672f667265657473615f6370732e68746d6c30\
3206082b060105050702011626687474703a2f2f7777772e667265657473612e6f72\
672f667265657473615f6370732e706466304706082b06010505070202303b1a3946\
72656554534120747275737465642074696d657374616d70696e6720536f66747761\
72652061732061205365727669636520285361615329300d06092a864886f70d0101\
0d05000382020100a5c944e2c6fac0a14d930a7fd0a0b172b41fc1483c3e957c68a2\
bcd9b9764f1a950161fd72472d41a5eed277786203b5422240fb3a26cde176087b6f\
b1011df4cc19e2571aa4a051109665e94c46f50bd2adee6ac4137e251b25a39dabda\
451515d8ff9e07209e8ec20b7874f7e1a0ede7c00937fe84a334f8b3265ced2d8ed9\
df61396583677feb382c1ee3b23e6ea5f05df30de7b9f89005d25266f612f39c8b4f\
6daba6d7bfbac19632b90637329f52a6f066a10e43eaa81f849a6c5fe3fe8b5ea232\
75f687f2052e502ea6c30762a668cce07871dd8e97e315bba929e25589977a0a312c\
e96c5106b1437c779f2b361b182888f3ee8a234374fa063e956192627f7c43107396\
5d1260928eba009e803429ae324cf96f042354f37bca5afddc79f79346ab388bfc79\
f01dc9861254ea6cc129941076b83d20556f3be51326837f2876f7833b370e7c3d41\
0523827d4f53400c72218d75229ff10c6f8893a9a3a1c0c42bb4c898c13df41c7f65\
73b4fc56515971a610a7b0d2857c8225a9fb204eaceca2e8971aa1af87886a2ae3c7\
2fe0a0aae842980a77bef16b92115458090d982b5946603764e75a0ad3d11454b998\
6f678b9ab6afe8497033ae3abfd4eb43b7bc9dee68815949e6481582a82e785277f2\
282107efe390200e0508acb8ea82ea2505276f3c9da2a3d3b4ad38bbf8842bda36fc\
2448291f558dc02dd1e0308207ff308205e7a003020102020900c1e986160da8e980\
300d06092a864886f70d01010d05003081953111300f060355040a13084672656520\
5453413110300e060355040b1307526f6f74204341311830160603550403130f7777\
772e667265657473612e6f72673122302006092a864886f70d010901161362757369\
6c657a617340676d61696c2e636f6d3112301006035504071309577565727a627572\
67310f300d0603550408130642617965726e310b3009060355040613024445301e17\
0d3136303331333031353231335a170d3431303330373031353231335a3081953111\
300f060355040a130846726565205453413110300e060355040b1307526f6f742043\
41311830160603550403130f7777772e667265657473612e6f72673122302006092a\
864886f70d0109011613627573696c657a617340676d61696c2e636f6d3112301006\
035504071309577565727a62757267310f300d0603550408130642617965726e310b\
300906035504061302444530820222300d06092a864886f70d01010105000382020f\
003082020a0282020100b6028e0e3032f11110d964cda94b9d0278e1942ae913aaa5\
9907cda69793995bd9ac7e33bad9fe3704da1c01a98d21afe3f591a59d7067705167\
998f5016722e0ab462b21f439171d2cfcc4593f3735af794a5ab311f6c010c7898de\
33d75c4510ee76f4bd1d1498cf17d303f06a5dd9f796cc6ca9b657a56fe3ea4fefbe\
7ce6b6a18d3e35a30cee5ff170d1cf39a333d3fda8964d22db685b29e561be890f0a\
a845873b2e84ab26ab839ffe8fade9d23bb31e61d273cc9b880649185fabecfa0534\
600aba901b614e2e854582dea2226fc19cd7df52bed50d8777cd9988c053a3fc7dc3\
287a068a4ff12b713cd9803666e955385456ff38f80298cf6b93856e9224774a66cf\
1cdd11c2f8efd85203d7458b25664b13ed639cded4ff8113d6cc5353d2729473c3c3\
07157c722aa5b5dd0bfb2d6c38b1b93749c881ec60026d08951b3824bd71bacbce47\
3aebd636f0b918b4a2c8ff4694f07457af2d6f1cf82554d1770fd79ff5d314dcd104\
cddcabc94138056dfcf017e7eb8572fd52f70144f188da05f5823f58dd06297e7387\
bed2d772c13da8266601045fe412dd70986c0c987ba7344b9037387516d258e7885b\
51f8968b7f2601213bc4cb4c85f8ff0b84af6a988337cdfb81868f7ecf31dca6716d\
7ec2dd802c1672629e5c0052cb357dd29aafc43f615b3b1ff9d4e1ce08c71c73e1fe\
bb7dc56a33621329e9ed6c230203010001a382024e3082024a300c0603551d130405\
30030101ff300e0603551d0f0101ff0404030201c6301d0603551d0e04160414fa55\
0d8c346651434cf7e7b3a76c95af7ae6a4973081ca0603551d230481c23081bf8014\
fa550d8c346651434cf7e7b3a76c95af7ae6a497a1819ba481983081953111300f06\
0355040a130846726565205453413110300e060355040b1307526f6f742043413118\
30160603550403130f7777772e667265657473612e6f72673122302006092a864886\
f70d0109011613627573696c657a617340676d61696c2e636f6d3112301006035504\
071309577565727a62757267310f300d0603550408130642617965726e310b300906\
0355040613024445820900c1e986160da8e98030330603551d1f042c302a3028a026\
a0248622687474703a2f2f7777772e667265657473612e6f72672f726f6f745f6361\
2e63726c3081cf0603551d200481c73081c43081c1060a2b0601040181f224010130\
81b2303306082b060105050702011627687474703a2f2f7777772e66726565747361\
2e6f72672f667265657473615f6370732e68746d6c303206082b0601050507020116\
26687474703a2f2f7777772e667265657473612e6f72672f667265657473615f6370\
732e706466304706082b06010505070202303b1a3946726565545341207472757374\
65642074696d657374616d70696e6720536f66747761726520617320612053657276\
69636520285361615329303706082b06010505070101042b3029302706082b060105\
05073001861b687474703a2f2f7777772e667265657473612e6f72673a3235363030\
0d06092a864886f70d01010d0500038202010068af7ebf938562ef4ceb3b580be2fa\
f6cc35a26772962f3d95901fa5630c87d09198984ce8a06a33f8a9c282ed9f1cb11a\
c6c23e17108ee4efce6fb294de95c133262255725522ca61971d4a3b7f78250dfb8d\
4aeec0fb1959b164100520b9c10e64c62662e4ad4d0abae2298fc948fc4e99e8d9e6\
b8fdbe4404121ec7c1422eacb2c9d7328e07396e60b4f3bb803ad4a555c80fefb53f\
85e7764a0a9fb4afc399f4cd2f5fbf587105c6081cf3d05337b6bb7d1b010b749f48\
88c912f3696ba1b6902d77b7dfc046c04a0cc1ec4f8d185e2da55dfb7bc2a2036c62\
19246a4f99ddbb6f1f829398f3b803dc0ad90dcb59bef4c27c77404b99043b782718\
67991152c399f12cbfc4c625adc096355ae44e342100ec517a502e2f06f940b8d435\
99bbc1154f8ae761a0b0d555fb4a1391d4f3420af8dbf12f2d7ddb9d77dce1537804\
074af175e4f2d6d55b34b5d6f7dcbdd31730af56480d4c0cff143f9e83bc151866d0\
ba0f0bbdc47fe27864176bbd6c1ab85df325edf777889bc4471bf3fa73e56cc591e8\
b160cda7b0786a1ec04ac3b24fa2e28d5d19e5e48004d5e166a83c82ec6fd54fb385\
ebaf7133a85b52de46db5244e1c34ae8d36e712f9fce0d493d7d3edd586c6198e3ec\
3e6e96346f417ac9f221e0aff33a8f6a0b1ef4c023630b76adaa8d91433825ecc41c\
49a5b98b181c7da30e997ab954c73c2cd805afda993182038a308203860201013081\
a33081953111300f060355040a130846726565205453413110300e060355040b1307\
526f6f74204341311830160603550403130f7777772e667265657473612e6f726731\
22302006092a864886f70d0109011613627573696c657a617340676d61696c2e636f\
6d3112301006035504071309577565727a62757267310f300d060355040813064261\
7965726e310b3009060355040613024445020900c1e986160da8e982300d06096086\
480165030402030500a081b8301a06092a864886f70d010903310d060b2a864886f7\
0d0109100104301c06092a864886f70d010905310f170d3235303131383131323030\
365a302b060b2a864886f70d010910020c311c301a301830160414916da3d860ecca\
82e34bc59d1793e7e968875f14304f06092a864886f70d01090431420440d26c8a6d\
b748885b0cd9c4ff636cb5d3c7f81308ea3c0bd8f76ab2112b21c1ec762c8f0318ca\
477472ab2bfde5c9d25129a2b144734b1766c094d66d3aa24d19300d06092a864886\
f70d0101010500048202009808366698a20227b3a03017317dbcd3813c7ec8f29693\
9ef20082bcdb95e8ed0495f299c2c6484b2246ab81092c73d039b0e33647a9241df1\
35fd44b9860c26cc784463d292e79ce39d04c0cffb0f2fb7cc9220ca3cbe43b088e4\
355dd7fc38a22ef9ad80629b15cd82e861b57df8797a3968f760b0175151aa3dd2c3\
7aaf8361571441295157c063af57ee66031870d80f30696da7b130a0d07e8753d517\
3e773713e28eec29b6999e17e65de2b20a0d2a4c33bf0734d7463da3c67da1c76353\
028761f0f2eaab1525bc489525d6ed34b34ae00a7ce34ceefaa6df08026047e470e3\
09d0507832b65dad717287dcef8c250d7d7ddf677dd3a6c267c2d29c86e04653ce84\
f7376c2434e2e85ec0eeaf2031a5f8cb4025f13b67c3ed4062af46000dbb1e3b5699\
d14cb309c8cdabb736651b76957cb4392f9e2452a88233936e39bd23dae37eeee3de\
4733a1ce2545324deb8a2203eed8264e3d657e60479cc08fa93916c266dcd1027daa\
1afd091bde8bea923d92b6e17615eb9f83210c4f2b6fcecb918cfa638a75679aa3df\
b5f959edc50923ff70c0d45a647a714f01ea48d803f68bb5081c97a57dcbd00c15d9\
44ba3a89e126bec18b9f49c0225cab0c9e9a9b24de43e5e767b7512a525d909a52e5\
cb2d79f5221d4f056e60dafb1dcc6e46f6dd1bb553d8caa37ee6add7c1dc70796766\
d126e88b37d69fec915aa3dd65'}>>,
{4: '11'},
'This is the content.',
h'\
1b512caa05005b7a2329c1b92cc5447de3a387acc2537ec579d26d38c5be8740ed85\
b8d3888630cc080b5eaaad12c029cde6117599565e63ca8485e927958682'
])
¶
Starting with the following COSE_Sign1 object¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
18(
[
/ protected h'a10126' / << {
/ alg / 1:-7 / ECDSA 256 /
} >>,
/ unprotected / {
/ kid / 4:'11'
},
/ payload / 'This is the content.',
/ signature / h'\
8eb33e4ca31d1c465ab05aac34cc6b23d58fef5c083106c4d25a91aef0b0117e2af9\
a291aa32e14ab834dc56ed2a223444547e01f11d3b0916e5a4c345cacb36'
]
)
¶
The CBOR-encoded signature field is hashed using SHA-256 to create the following TimeStampReq object¶
SEQUENCE {
INTEGER 1
SEQUENCE {
SEQUENCE {
OBJECT IDENTIFIER sha-256 (2 16 840 1 101 3 4 2 1)
NULL
}
OCTET STRING
44 C2 41 9D 13 1D 53 D5 55 84 B5 DD 33 B7 88 C2
4E 55 1C 6D 44 B1 AF C8 B2 B8 5E 69 54 76 3B 4E
}
BOOLEAN TRUE
}
¶
which is sent to the Time Stamping Authority.¶
A TimeStampResp is returned which contains the following TimeStampToken¶
SEQUENCE {
OBJECT IDENTIFIER signedData (1 2 840 113549 1 7 2)
[0] {
SEQUENCE {
INTEGER 3
SET {
SEQUENCE {
OBJECT IDENTIFIER sha-512 (2 16 840 1 101 3 4 2 3)
NULL
}
}
SEQUENCE {
OBJECT IDENTIFIER tSTInfo (1 2 840 113549 1 9 16 1 4)
[0] {
OCTET STRING, encapsulates {
SEQUENCE {
INTEGER 1
OBJECT IDENTIFIER '1 2 3 4 1'
SEQUENCE {
SEQUENCE {
OBJECT IDENTIFIER sha-256 (2 16 840 1 101 3 4 2 1)
NULL
}
OCTET STRING
44 C2 41 9D 13 1D 53 D5 55 84 B5 DD 33 B7 88 C2
4E 55 1C 6D 44 B1 AF C8 B2 B8 5E 69 54 76 3B 4E
}
INTEGER 84895155
GeneralizedTime 17/01/2025 18:29:13 GMT
BOOLEAN TRUE
[...]
¶
The contents of the TimeStampToken are bstr-wrapped and added to the unprotected headers bucket in the original COSE_Sign1 object to obtain the following¶
=============== NOTE: '\' line wrapping per RFC 8792 ================
18(
[
/ protected h'a10126' / << {
/ alg / 1:-7 / ECDSA 256 /
} >>,
/ unprotected / {
/ 3161-ctt / 259 : h'\
3082154906092a864886f70d010702a082153a30821536020103310f300d06096086\
48016503040203050030820184060b2a864886f70d0109100104a08201730482016f\
3082016b02010106042a0304013031300d06096086480165030402010500042044c2\
419d131d53d55584b5dd33b788c24e551c6d44b1afc8b2b85e6954763b4e0204050f\
65b3180f32303235303131373138323931335a0101ffa0820111a482010d30820109\
3111300f060355040a13084672656520545341310c300a060355040b130354534131\
763074060355040d136d54686973206365727469666963617465206469676974616c\
6c79207369676e7320646f63756d656e747320616e642074696d65207374616d7020\
7265717565737473206d616465207573696e672074686520667265657473612e6f72\
67206f6e6c696e65207365727669636573311830160603550403130f7777772e6672\
65657473612e6f72673122302006092a864886f70d0109011613627573696c657a61\
7340676d61696c2e636f6d3112301006035504071309577565727a62757267310b30\
09060355040613024445310f300d0603550408130642617965726ea0821008308208\
01308205e9a003020102020900c1e986160da8e982300d06092a864886f70d01010d\
05003081953111300f060355040a130846726565205453413110300e060355040b13\
07526f6f74204341311830160603550403130f7777772e667265657473612e6f7267\
3122302006092a864886f70d0109011613627573696c657a617340676d61696c2e63\
6f6d3112301006035504071309577565727a62757267310f300d0603550408130642\
617965726e310b3009060355040613024445301e170d313630333133303135373339\
5a170d3236303331313031353733395a308201093111300f060355040a1308467265\
6520545341310c300a060355040b130354534131763074060355040d136d54686973\
206365727469666963617465206469676974616c6c79207369676e7320646f63756d\
656e747320616e642074696d65207374616d70207265717565737473206d61646520\
7573696e672074686520667265657473612e6f7267206f6e6c696e65207365727669\
636573311830160603550403130f7777772e667265657473612e6f72673122302006\
092a864886f70d0109011613627573696c657a617340676d61696c2e636f6d311230\
1006035504071309577565727a62757267310b3009060355040613024445310f300d\
0603550408130642617965726e30820222300d06092a864886f70d01010105000382\
020f003082020a0282020100b591048c4e486f34e9dc08627fc2375162236984b82c\
b130beff517cfc38f84bce5c65a874dab2621ae0bce7e33563e0ede934fd5f882315\
9f07848808227460c1ed88261706f4281334359dfbb81bd1353fc179610af1a8c8c8\
65dc00ea23b3a89be6bd03ba85a9ec827d60565905e22d6a584ed1380ae150280cee\
397e98a012f380464007862443bc077cb95f421af31712d9683cdb6dffbaf3c8ba5b\
a566ae523d459d6177346d4d840e27886b7c01c5b890d78a2e27bba8dd2f9a2812e1\
57d62f921c65962548069dcdb7d06de181de0e9570d66f87220ce28b628ab55906f3\
ee0c210f7051e8f4858af8b9a92d09e46af2d9cba5bfcfad168cdf604491a4b06603\
b114caf7031f065e7eeefa53c575f3490c059d2e32ddc76ac4d4c4c710683b97fd1b\
e591bc61055186d88f9a0391b307b6f91ed954daa36f9acd6a1e14aa2e4adf17464b\
54db18dbb6ffe30080246547370436ce4e77bae5de6fe0f3f9d6e7ffbeb461e794e9\
2fb0951f8aae61a412cce9b21074635c8be327ae1a0f6b4a646eb0f8463bc63bf845\
530435d19e802511ec9f66c3496952d8becb69b0aa4d4c41f60515fe7dcbb89319cd\
da59ba6aea4be3ceae718e6fcb6ccd7db9fc50bb15b12f3665b0aa307289c2e6dd4b\
111ce48ba2d9efdb5a6b9a506069334fb34f6fc7ae330f0b34208aac80df3266fdd9\
0465876ba2cb898d9505315b6e7b0203010001a38201db308201d730090603551d13\
04023000301d0603551d0e041604146e760b7b4e4f9ce160ca6d2ce927a2a294b377\
37301f0603551d23041830168014fa550d8c346651434cf7e7b3a76c95af7ae6a497\
300b0603551d0f0404030206c030160603551d250101ff040c300a06082b06010505\
070308306306082b0601050507010104573055302a06082b06010505073002861e68\
7474703a2f2f7777772e667265657473612e6f72672f7473612e637274302706082b\
06010505073001861b687474703a2f2f7777772e667265657473612e6f72673a3235\
363030370603551d1f0430302e302ca02aa0288626687474703a2f2f7777772e6672\
65657473612e6f72672f63726c2f726f6f745f63612e63726c3081c60603551d2004\
81be3081bb3081b80601003081b2303306082b060105050702011627687474703a2f\
2f7777772e667265657473612e6f72672f667265657473615f6370732e68746d6c30\
3206082b060105050702011626687474703a2f2f7777772e667265657473612e6f72\
672f667265657473615f6370732e706466304706082b06010505070202303b1a3946\
72656554534120747275737465642074696d657374616d70696e6720536f66747761\
72652061732061205365727669636520285361615329300d06092a864886f70d0101\
0d05000382020100a5c944e2c6fac0a14d930a7fd0a0b172b41fc1483c3e957c68a2\
bcd9b9764f1a950161fd72472d41a5eed277786203b5422240fb3a26cde176087b6f\
b1011df4cc19e2571aa4a051109665e94c46f50bd2adee6ac4137e251b25a39dabda\
451515d8ff9e07209e8ec20b7874f7e1a0ede7c00937fe84a334f8b3265ced2d8ed9\
df61396583677feb382c1ee3b23e6ea5f05df30de7b9f89005d25266f612f39c8b4f\
6daba6d7bfbac19632b90637329f52a6f066a10e43eaa81f849a6c5fe3fe8b5ea232\
75f687f2052e502ea6c30762a668cce07871dd8e97e315bba929e25589977a0a312c\
e96c5106b1437c779f2b361b182888f3ee8a234374fa063e956192627f7c43107396\
5d1260928eba009e803429ae324cf96f042354f37bca5afddc79f79346ab388bfc79\
f01dc9861254ea6cc129941076b83d20556f3be51326837f2876f7833b370e7c3d41\
0523827d4f53400c72218d75229ff10c6f8893a9a3a1c0c42bb4c898c13df41c7f65\
73b4fc56515971a610a7b0d2857c8225a9fb204eaceca2e8971aa1af87886a2ae3c7\
2fe0a0aae842980a77bef16b92115458090d982b5946603764e75a0ad3d11454b998\
6f678b9ab6afe8497033ae3abfd4eb43b7bc9dee68815949e6481582a82e785277f2\
282107efe390200e0508acb8ea82ea2505276f3c9da2a3d3b4ad38bbf8842bda36fc\
2448291f558dc02dd1e0308207ff308205e7a003020102020900c1e986160da8e980\
300d06092a864886f70d01010d05003081953111300f060355040a13084672656520\
5453413110300e060355040b1307526f6f74204341311830160603550403130f7777\
772e667265657473612e6f72673122302006092a864886f70d010901161362757369\
6c657a617340676d61696c2e636f6d3112301006035504071309577565727a627572\
67310f300d0603550408130642617965726e310b3009060355040613024445301e17\
0d3136303331333031353231335a170d3431303330373031353231335a3081953111\
300f060355040a130846726565205453413110300e060355040b1307526f6f742043\
41311830160603550403130f7777772e667265657473612e6f72673122302006092a\
864886f70d0109011613627573696c657a617340676d61696c2e636f6d3112301006\
035504071309577565727a62757267310f300d0603550408130642617965726e310b\
300906035504061302444530820222300d06092a864886f70d01010105000382020f\
003082020a0282020100b6028e0e3032f11110d964cda94b9d0278e1942ae913aaa5\
9907cda69793995bd9ac7e33bad9fe3704da1c01a98d21afe3f591a59d7067705167\
998f5016722e0ab462b21f439171d2cfcc4593f3735af794a5ab311f6c010c7898de\
33d75c4510ee76f4bd1d1498cf17d303f06a5dd9f796cc6ca9b657a56fe3ea4fefbe\
7ce6b6a18d3e35a30cee5ff170d1cf39a333d3fda8964d22db685b29e561be890f0a\
a845873b2e84ab26ab839ffe8fade9d23bb31e61d273cc9b880649185fabecfa0534\
600aba901b614e2e854582dea2226fc19cd7df52bed50d8777cd9988c053a3fc7dc3\
287a068a4ff12b713cd9803666e955385456ff38f80298cf6b93856e9224774a66cf\
1cdd11c2f8efd85203d7458b25664b13ed639cded4ff8113d6cc5353d2729473c3c3\
07157c722aa5b5dd0bfb2d6c38b1b93749c881ec60026d08951b3824bd71bacbce47\
3aebd636f0b918b4a2c8ff4694f07457af2d6f1cf82554d1770fd79ff5d314dcd104\
cddcabc94138056dfcf017e7eb8572fd52f70144f188da05f5823f58dd06297e7387\
bed2d772c13da8266601045fe412dd70986c0c987ba7344b9037387516d258e7885b\
51f8968b7f2601213bc4cb4c85f8ff0b84af6a988337cdfb81868f7ecf31dca6716d\
7ec2dd802c1672629e5c0052cb357dd29aafc43f615b3b1ff9d4e1ce08c71c73e1fe\
bb7dc56a33621329e9ed6c230203010001a382024e3082024a300c0603551d130405\
30030101ff300e0603551d0f0101ff0404030201c6301d0603551d0e04160414fa55\
0d8c346651434cf7e7b3a76c95af7ae6a4973081ca0603551d230481c23081bf8014\
fa550d8c346651434cf7e7b3a76c95af7ae6a497a1819ba481983081953111300f06\
0355040a130846726565205453413110300e060355040b1307526f6f742043413118\
30160603550403130f7777772e667265657473612e6f72673122302006092a864886\
f70d0109011613627573696c657a617340676d61696c2e636f6d3112301006035504\
071309577565727a62757267310f300d0603550408130642617965726e310b300906\
0355040613024445820900c1e986160da8e98030330603551d1f042c302a3028a026\
a0248622687474703a2f2f7777772e667265657473612e6f72672f726f6f745f6361\
2e63726c3081cf0603551d200481c73081c43081c1060a2b0601040181f224010130\
81b2303306082b060105050702011627687474703a2f2f7777772e66726565747361\
2e6f72672f667265657473615f6370732e68746d6c303206082b0601050507020116\
26687474703a2f2f7777772e667265657473612e6f72672f667265657473615f6370\
732e706466304706082b06010505070202303b1a3946726565545341207472757374\
65642074696d657374616d70696e6720536f66747761726520617320612053657276\
69636520285361615329303706082b06010505070101042b3029302706082b060105\
05073001861b687474703a2f2f7777772e667265657473612e6f72673a3235363030\
0d06092a864886f70d01010d0500038202010068af7ebf938562ef4ceb3b580be2fa\
f6cc35a26772962f3d95901fa5630c87d09198984ce8a06a33f8a9c282ed9f1cb11a\
c6c23e17108ee4efce6fb294de95c133262255725522ca61971d4a3b7f78250dfb8d\
4aeec0fb1959b164100520b9c10e64c62662e4ad4d0abae2298fc948fc4e99e8d9e6\
b8fdbe4404121ec7c1422eacb2c9d7328e07396e60b4f3bb803ad4a555c80fefb53f\
85e7764a0a9fb4afc399f4cd2f5fbf587105c6081cf3d05337b6bb7d1b010b749f48\
88c912f3696ba1b6902d77b7dfc046c04a0cc1ec4f8d185e2da55dfb7bc2a2036c62\
19246a4f99ddbb6f1f829398f3b803dc0ad90dcb59bef4c27c77404b99043b782718\
67991152c399f12cbfc4c625adc096355ae44e342100ec517a502e2f06f940b8d435\
99bbc1154f8ae761a0b0d555fb4a1391d4f3420af8dbf12f2d7ddb9d77dce1537804\
074af175e4f2d6d55b34b5d6f7dcbdd31730af56480d4c0cff143f9e83bc151866d0\
ba0f0bbdc47fe27864176bbd6c1ab85df325edf777889bc4471bf3fa73e56cc591e8\
b160cda7b0786a1ec04ac3b24fa2e28d5d19e5e48004d5e166a83c82ec6fd54fb385\
ebaf7133a85b52de46db5244e1c34ae8d36e712f9fce0d493d7d3edd586c6198e3ec\
3e6e96346f417ac9f221e0aff33a8f6a0b1ef4c023630b76adaa8d91433825ecc41c\
49a5b98b181c7da30e997ab954c73c2cd805afda993182038a308203860201013081\
a33081953111300f060355040a130846726565205453413110300e060355040b1307\
526f6f74204341311830160603550403130f7777772e667265657473612e6f726731\
22302006092a864886f70d0109011613627573696c657a617340676d61696c2e636f\
6d3112301006035504071309577565727a62757267310f300d060355040813064261\
7965726e310b3009060355040613024445020900c1e986160da8e982300d06096086\
480165030402030500a081b8301a06092a864886f70d010903310d060b2a864886f7\
0d0109100104301c06092a864886f70d010905310f170d3235303131373138323931\
335a302b060b2a864886f70d010910020c311c301a301830160414916da3d860ecca\
82e34bc59d1793e7e968875f14304f06092a864886f70d010904314204405f98e6ad\
02a79c3209de2048fbf258d852df9f13c9ebef826154ef27fe4325a96d868c99e083\
8791ac37faf028647f94abab446f3a93a9a0f51431a6e3d36c34300d06092a864886\
f70d010101050004820200243d5af44af116c62c6053076eb6283a2b73beafa5411e\
aee73dcc273e1b6327ab917c75bdec1305d2680e899a160e2b42a05f330bdf44c54f\
1796ba538a3abfdab04cef3bba22ea4767bd30925c42c0ab91b5929b7a9aa99f3876\
f5c8b1da1a98c7cb1f959394f9d707fa7ec04fb6943059cc98d04653b6f8e967a1eb\
29269caca57c9fdd5294b54d595b58541a9ec14b5a0e9484573c5568b4943a7df4ff\
c101cd807d66f3a869b363fdd87be9854a8260c0877acccf3b42618b8948191ff36e\
999842c2569c44f189d8ab9f587bb54222be7d20926b3312882352efe5d50f46647a\
149b4e0c59cbaaddd5ba0ce22715e4ee09c82bee3a83dc86d85192912ecfb005ce0e\
b28a6549f92aa8ae9beb63eb8fadabe7eca3be5ccc6b2cb4e55d803fc76682bf82b1\
de06e97ed9a272ded198f0370cea6f59d2c1927f2c0667308fedf41ac565d3333dec\
5065daddd2c89d75261f52bfad5f87b48140f39ff12ef0c4d571085f72d94eb0a9d8\
d65bf5ece1cad4e65452d8abe083f60ff977f247df79c263bbd32bdc7c5aae9da84d\
a7d1a93b4193bd1f287a0a32c06c015d66cdf36b29d2b289c1484e720982190eef9c\
2cc58c4fac9bd99089d1ad6960c5d06c992c4936e5b22495743dfbd1fda6ed2475b3\
d445fd8dde40bb09e624c77d5d97faf1a88b44dda8ce7735f2482f822acf68027e6b\
ca81532e740cb0824ca501504b',
/ kid / 4:'11'
},
/ payload / 'This is the content.',
/ signature / h'8eb33e4ca31d1c465ab05aac34cc6b23d58fef5c083106c4
d25a91aef0b0117e2af9a291aa32e14ab834dc56ed2a223444547e01f11d3b0916e5
a4c345cacb36'
]
)
¶
The editors would like to thank Carl Wallace, Carsten Bormann, Francesca Palombini, Leonard Rosenthol, Linda Dunbar, Michael B. Jones, Michael Prorock, Orie Steele, Shuping Peng, Steve Lasker, and Yingzhen Qu for their reviews and comments.¶
Carsten contributed part of the security considerations.¶
Orie contributed an improved version of the diagrams.¶