draft-ietf-cose-hash-algs-00.txt   draft-ietf-cose-hash-algs-01.txt 
Network Working Group J. Schaad Network Working Group J. Schaad
Internet-Draft August Cellars Internet-Draft August Cellars
Intended status: Informational 11 March 2019 UpdatesRFC8152 (if approved) June 10, 2019
Expires: 12 September 2019 Intended status: Informational
Expires: December 12, 2019
CBOR Object Signing and Encryption (COSE): Hash Algorithms CBOR Object Signing and Encryption (COSE): Hash Algorithms
draft-ietf-cose-hash-algs-00 draft-ietf-cose-hash-algs-01
Abstract Abstract
The CBOR Object Signing and Encryption (COSE) syntax The CBOR Object Signing and Encryption (COSE) syntax RFC 8152 does
[I-D.ietf-cose-rfc8152bis-struct] does not define any direct methods not define any direct methods for using hash algorithms. There are
for using hash algorithms. There are however circumstances where however circumstances where hash algorithms are used: Indirect
hash algorithms are used: Indirect signatures where the hash of one signatures, where the hash of one or more external contents are
or more contents are signed. X.509 certificate or other object signed, or thumbprints, for identification of X.509 certificates or
identification by the use of a thumbprint. This document defines a other objects. This document defines a set of hash algorithms that
set of hash algorithms that are identified by COSE Algorithm are identified by COSE Algorithm Identifiers.
Identifiers.
Contributing to this document Contributing to this document
The source for this draft is being maintained in GitHub. Suggested The source for this draft is being maintained in GitHub. Suggested
changes should be submitted as pull requests at TBD. Editorial changes should be submitted as pull requests at https://github.com/
changes can be managed in GitHub, but any substantial issues need to cose-wg/X509 Editorial changes can be managed in GitHub, but any
be discussed on the COSE mailing list. substantial issues need to be discussed on the COSE mailing list.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on 12 September 2019. This Internet-Draft will expire on December 12, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Terminology 1.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
1.2. Open Issues 1.2. Open Issues . . . . . . . . . . . . . . . . . . . . . . . 3
2. Hash Algorithm Identifiers 2. Hash Algorithm Usage . . . . . . . . . . . . . . . . . . . . 3
2.1. SHA-1 Hash Algorithm 2.1. Example CBOR hash structure . . . . . . . . . . . . . . . 4
2.2. SHA-2 Hash Algorithms 3. Hash Algorithm Identifiers . . . . . . . . . . . . . . . . . 5
2.3. SHAKE Algorithms 3.1. SHA-1 Hash Algorithm . . . . . . . . . . . . . . . . . . 5
3. IANA Considerations 3.2. SHA-2 Hash Algorithms . . . . . . . . . . . . . . . . . . 6
3.1. COSE Algorithm Registry 3.3. SHAKE Algorithms . . . . . . . . . . . . . . . . . . . . 7
4. Security Considerations 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5. Normative References 4.1. COSE Algorithm Registry . . . . . . . . . . . . . . . . . 8
6. Informative References 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
Author's Address 6. Normative References . . . . . . . . . . . . . . . . . . . . 9
7. Informative References . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
The CBOR Object Signing and Encryption (COSE) syntax does not define The CBOR Object Signing and Encryption (COSE) syntax does not define
any direct methods for the use of hash algorithms. It also does not any direct methods for the use of hash algorithms. It also does not
define a structure syntax that is used to encode a digested object define a structure syntax that is used to encode a digested object
structure along the lines of the DigestedData ASN.1 structure in structure along the lines of the DigestedData ASN.1 structure in
[CMS]. This omission was intentional as a structure consisting of [CMS]. This omission was intentional as a structure consisting of
jut a digest identifier, the content, and a digest value does not by just a digest identifier, the content, and a digest value does not by
itself provide any strong security service. Additional, an itself provide any strong security service. Additionally, an
application is going to be better off defining this type of structure application is going to be better off defining this type of structure
so that it can add any additional data that needs to be hashed as so that it can include add any additional data that needs to be
well as methods of obtaining the data. hashed, as well as methods of obtaining the data.
While the above is true, there are some cases where having some While the above is true, there are some cases where having some
standard hash algorithms defined for COSE with a common identifier standard hash algorithms defined for COSE with a common identifier
makes a great deal of sense. Two of the cases where these are going makes a great deal of sense. Two of the cases where these are going
to be used are: to be used are:
* Indirect signing of content, and * Indirect signing of content, and
* Object identification. * Object identification.
skipping to change at line 122 skipping to change at page 3, line 30
1.1. Requirements Terminology 1.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
1.2. Open Issues 1.2. Open Issues
* Are there additional SHA-2 formulations that need to be added or RFC Editor: Please remove this section before publishing.
should some of the ones in this document be removed?
* Should additional hash algorithms be added to the document? * No Open Issues
* Review the Recommended column in all of the tables to make sure 2. Hash Algorithm Usage
that the values are correct.
* Are there recommendations that should be provided on what range of As noted in the previous section, hash functions can be used for a
identifiers should be used for these algorithms? Inputs would variety of purposes. Some of these purposes require that a hash
include the expected frequency of use for each algorithm. function be cryptographically strong, these include direct and
indirect signatures. That is, using the hash as part of the
signature or using the hash as part of the body to be signed. Other
uses of hash functions do not require the same level of strength.
2. Hash Algorithm Identifiers This document contains some hash functions that are not designed to
be used for cryptographic operations. An application that is using a
hash function needs to carefully evaluate exactly what hash
properties are needed and which hash functions are going to provide
them. Applications should also make sure that the ability to change
hash functions is part of the base design as cryptographic advances
are sure to reduce strength of a hash function.
2.1. SHA-1 Hash Algorithm A hash function is a map from a large bit string to a smaller bit
string. There are going to be collisions by a hash function, the
trick is to make sure that it is difficult to find two values that
are going to map to the same output value. The standard "Collision
Attack" is one where an attacker can find two different messages that
have the same hash value. If a collision attack exists, then the
function SHOULD NOT be used for a cryptographic purpose. The only
reason why such a hash function is used is when there is absolutely
no other choice (e.g. a HSM that cannot be replaced), and only after
looking at the possible security issues. Cryptographic purposes
would include creation of signatures or the use of hashes for
indirect signatures. These functions may still be usable for non-
cryptographic purposes.
The SHA-1 hash algorithm [RFC3174] wsa designed by the United States An example of a non-cryptographic use of a hash is for filtering from
National Security Agenciy and published in 1995. Since that time a a collection of values to find possible candidates that can later be
checked to see if they are the correct one. A simple example of this
is the classic thumbprint of a certificate. If the thumbprint is
used to verify that it is the correct certificate, then that usage is
subject to a collision attack as above. If however, the thumbprint
is used to sort through a collection of certificates to find those
that might be used for the purpose of verifying a signature, a simple
filter capability is sufficient. In this case, one still needs to
validate that the public key validates the signature (and the
certificate is trusted), and all certificates that don't contain a
key that validates the signature can be discarded as false positives.
To distinguish between these two cases, a new value in the
recommended column of the COSE Algorithms registry is to be added.
"Filter Only" indicates that the only purpose of a hash function
should be to filter results and not those which require collision
resistance.
2.1. Example CBOR hash structure
[COSE] did not provide a default structure for holding a hash value
not only because no separate hash algorithms were defined, but
because how the structure is setup is frequently application
specific. There are four fields that are often included as part of a
hash structure:
* The hash algorithm identifier.
* The hash value.
* A pointer to the value that was hashed, this could be a pointer to
a file, an object that can be obtained from the network, or a
pointer to someplace in the message, or something very application
specific.
* Additional data, this can be something as simple as a random value
to make finding hash collisions slightly harder as the value
handed to the application cannot have been selected to have a
collision, or as complicated as a set of processing instructions
that are to be used with the object that is pointed to.
An example of a structure which permits all of the above fields to
exist would look like the following. There is no definition here of
what goes into the 'any' value and how it would be included in the
computed hash value.
COSE_Hash_V = ( 1 : int / tstr, # Algorithm identifier 2 : bstr, # Hash value 3 : tstr ?, # Location of object hashed 4 : any ? # object containing other details and things - prefixed to the object to be hashed )
An alternate structure that could be used for situations where one is
searching a group of objects for a match. In this case, the location
would not be needed and adding extra data to the hash would be
counterproductive. This results in a structure that looks like this:
COSE_Hash_Find = [ hashAlg : int / tstr, hashValue : bstr ]
3. Hash Algorithm Identifiers
3.1. SHA-1 Hash Algorithm
The SHA-1 hash algorithm [RFC3174] was designed by the United States
National Security Agency and published in 1995. Since that time a
large amount of cryptographic analysis has been applied to this large amount of cryptographic analysis has been applied to this
algorithm and a successful collision attack has been created algorithm and a successful collision attack has been created
([SHA-1-collision]). The IETF formally started discouraging the use ([SHA-1-collision]). The IETF formally started discouraging the use
of SHA-1 with the publishing of [RFC6194]. of SHA-1 with the publishing of [RFC6194].
Dispite the above, there are still times where SHA-1 needs to be used Despite the above, there are still times where SHA-1 needs to be used
and therefore it makes sense to assign a point for the use of this and therefore it makes sense to assign a point for the use of this
hash algorithm. Some of these situations are with historic HSMs hash algorithm. Some of these situations are with historic HSMs
where only SHA-1 is implemented or where the SHA-1 value is used for where only SHA-1 is implemented or where the SHA-1 value is used for
the purpose of filtering and thus the collision resistance property the purpose of filtering and thus the collision resistance property
is not needed. is not needed.
Because of the known issues for SHA-1 and the fact that is should no Because of the known issues for SHA-1 and the fact that is should no
longer be used, the algorithm will be registered with the longer be used, the algorithm will be registered with the
recommendation of "Depreciated". recommendation of "Filter Only".
+-------+-------+-------------+-----------------+-------------+ +-------+-------+-------------+-----------------+-------------+
| Name | Value | Description | Reference | Recommended | | Name | Value | Description | Reference | Recommended |
+=======+=======+=============+=================+=============+ +=======+=======+=============+=================+=============+
| SHA-1 | TBD6 | SHA-1 Hash | [This Document] | Depreciated | | SHA-1 | TBD6 | SHA-1 Hash | [This Document] | Filter Only |
+-------+-------+-------------+-----------------+-------------+ +-------+-------+-------------+-----------------+-------------+
Table 1: SHA-1 Hash Algorithm Table 1: SHA-1 Hash Algorithm
2.2. SHA-2 Hash Algorithms 3.2. SHA-2 Hash Algorithms
The family of SHA-2 hash algorithms [FIPS-180-4] was designed by the The family of SHA-2 hash algorithms [FIPS-180-4] was designed by the
United States National Security Agency and published in 2001. Since United States National Security Agency and published in 2001. Since
that time some additional algorithms have been added to the original that time some additional algorithms have been added to the original
set to deal with length extension attacks and some performance set to deal with length extension attacks and some performance
issues. While the SHA-3 hash algorithms has been published since issues. While the SHA-3 hash algorithms has been published since
that time, the SHA-2 algorithms are still broadly used. that time, the SHA-2 algorithms are still broadly used.
There are a number of different parameters for the SHA-2 hash There are a number of different parameters for the SHA-2 hash
functions. The set of hash functions which have been chosen for functions. The set of hash functions which have been chosen for
skipping to change at line 191 skipping to change at page 6, line 40
increase proportionally. Locations that use this hash function increase proportionally. Locations that use this hash function
need either to analysis the potential problems with having a need either to analysis the potential problems with having a
collision occur, or where the only function of the hash is to collision occur, or where the only function of the hash is to
narrow the possible choices. narrow the possible choices.
The latter is the case for [I-D.ietf-cose-x509], the hash value is The latter is the case for [I-D.ietf-cose-x509], the hash value is
used to select possible certificates and, if there are multiple used to select possible certificates and, if there are multiple
choices then, each choice can be tested by using the public key. choices then, each choice can be tested by using the public key.
* *SHA-256* is probably the most common hash function used * *SHA-256* is probably the most common hash function used
currently. SHA-256 is the most efficient hash algorithm for currently. SHA-256 is an efficient hash algorithm for 32-bit
32-bit hardware. hardware.
* *SHA-384* and *SHA-512* hash functions are more efficient when run * *SHA-384* and *SHA-512* hash functions are efficient for 64-bit
on 64-bit hardware. hardware.
* *SHA-512/256* provides a hash function that runs more efficiently * *SHA-512/256* provides a hash function that runs more efficiently
on 64-bit hardware, but offers the same security levels as SHA- on 64-bit hardware, but offers the same security levels as SHA-
256. 256.
+-------------+-------+----------------+-----------+-------------+ +-------------+-------+----------------+-----------+-------------+
| Name | Value | Description | Reference | Recommended | | Name | Value | Description | Reference | Recommended |
+=============+=======+================+===========+=============+ +=============+=======+================+===========+=============+
| SHA-256/64 | TBD1 | SHA-2 256-bit | [This | No | | SHA-256/64 | TBD1 | SHA-2 256-bit | [This | Filter Only |
| | | Hash truncated | Document] | | | | | Hash truncated | Document] | |
| | | to 64-bits | | | | | | to 64-bits | | |
+-------------+-------+----------------+-----------+-------------+ +-------------+-------+----------------+-----------+-------------+
| SHA-256 | TBD2 | SHA-2 256-bit | [This | Yes | | SHA-256 | TBD2 | SHA-2 256-bit | [This | Yes |
| | | Hash | Document] | | | | | Hash | Document] | |
+-------------+-------+----------------+-----------+-------------+ +-------------+-------+----------------+-----------+-------------+
| SHA-384 | TBD3 | SHA-2 384-bit | [This | Yes | | SHA-384 | TBD3 | SHA-2 384-bit | [This | Yes |
| | | Hash | Document] | | | | | Hash | Document] | |
+-------------+-------+----------------+-----------+-------------+ +-------------+-------+----------------+-----------+-------------+
| SHA-512 | TBD4 | SHA-2 512-bit | [This | Yes | | SHA-512 | TBD4 | SHA-2 512-bit | [This | Yes |
| | | Hash | Document] | | | | | Hash | Document] | |
+-------------+-------+----------------+-----------+-------------+ +-------------+-------+----------------+-----------+-------------+
| SHA-512/256 | TBD5 | SHA-2 512-bit | [This | Yes | | SHA-512/256 | TBD5 | SHA-2 512-bit | [This | Yes |
| | | Hash truncated | Document] | | | | | Hash truncated | Document] | |
| | | to 256-bits | | | | | | to 256-bits | | |
+-------------+-------+----------------+-----------+-------------+ +-------------+-------+----------------+-----------+-------------+
Table 2: SHA-2 Hash Algorithms Table 2: SHA-2 Hash Algorithms
2.3. SHAKE Algorithms 3.3. SHAKE Algorithms
The family SHA-3 hash algorithms [FIPS-180-4] was the result of a The family SHA-3 hash algorithms [FIPS-180-4] was the result of a
competition run by NIST. The pair of algorithms known as SHAKE-128 competition run by NIST. The pair of algorithms known as SHAKE-128
and SHAKE-256 are the instances of SHA-3 that are currently being and SHAKE-256 are the instances of SHA-3 that are currently being
standardized in the IETF. standardized in the IETF.
The SHA-3 hash algorithms have a significantly different structure The SHA-3 hash algorithms have a significantly different structure
than the SHA-3 hash algorithms. One of the benefits of this than the SHA-2 hash algorithms. One of the benefits of this
differences is that when computing a truncated SHAKE hash value, the differences is that when computing a shorter SHAKE hash value, the
value is not a prefix of a longer version of the same value. value is not a prefix of the result of computing the longer hash.
MAYBE TEXT: Might not need to define truncated versions of this hash Unlike the SHA-2 hash functions, no algorithm identifier is created
algorithm because the length of the resulting value is always going for shorter lengths. Applications can specify what the minimum
to generate a unique value since you cannot just truncate it like you length for a hash function for the protocol. A validator can infer
can with SHA-1 and SHA-2. the actual length from the hash value in these cases.
+----------+-------+---------------+-----------------+-------------+ +----------+-------+---------------+-----------------+-------------+
| Name | Value | Description | Reference | Recommended | | Name | Value | Description | Reference | Recommended |
+==========+=======+===============+=================+=============+ +==========+=======+===============+=================+=============+
| SHAKE128 | TBD10 | 128-bit SHAKE | [This Document] | Yes | | SHAKE128 | TBD10 | 128-bit SHAKE | [This Document] | Yes |
+----------+-------+---------------+-----------------+-------------+ +----------+-------+---------------+-----------------+-------------+
| SHAKE256 | TBD11 | 256-bit SHAKE | [This Document] | Yes | | SHAKE256 | TBD11 | 256-bit SHAKE | [This Document] | Yes |
+----------+-------+---------------+-----------------+-------------+ +----------+-------+---------------+-----------------+-------------+
Table 3: SHAKE Hash Functions Table 3: SHAKE Hash Functions
3. IANA Considerations 4. IANA Considerations
3.1. COSE Algorithm Registry 4.1. COSE Algorithm Registry
IANA is requested to register the following algorithms in the "COSE IANA is requested to register the following algorithms in the "COSE
Algorithms" registry. Algorithms" registry.
* The SHA-1 hash function found in Table 1. * The SHA-1 hash function found in Table 1.
* The set of SHA-2 hash functions found in Table 2. * The set of SHA-2 hash functions found in Table 2.
* The set of SHAKE hash functions found in Table 3. * The set of SHAKE hash functions found in Table 3.
Many of the hash values produced are relatively long and as such the Many of the hash values produced are relatively long and as such the
use of a two byte algorithm identifier seems reasonable. SHA-1 is use of a two byte algorithm identifier seems reasonable. SHA-1 is
tagged as deprecated and thus a longer algorithm identifier is tagged as deprecated and thus a longer algorithm identifier is
appropriate even though it is a shorter hash value. appropriate even though it is a shorter hash value.
4. Security Considerations In addition, IANA is to add the value of 'Filter Only' to the set of
legal values for the 'Recommended' column. This value is only to be
used for hash functions and indicates that it is not to be used for
purposes which require collision resistance.
There are security considerations: 5. Security Considerations
5. Normative References The security considerations have already been called out as part of
the previous text. The following issues need to be dealt with:
* Protocols need to perform a careful analysis of the properties of
a hash function that are needed and how they map onto the possible
attacks. In particular, one needs to distinguish between those
uses that need the cryptographic properties, i.e. collision
resistance, and properties that correspond to possible object
identification. The different attacks correspond to who or what
is being protected, is it the originator that is the attacker or a
third party? This is the difference between collision resistance
and second pre-image resistance. As a general rule, longer hash
values are "better" than short ones, but trade-offs of
transmission size, timeliness, and security all need to be
included as part of this analysis. In many cases the value being
hashed is a public value, as such pre-image resistance is not part
of this analysis.
* Algorithm agility needs to be considered a requirement for any use
of hash functions. As with any cryptographic function, hash
functions are under constant attack and the strength of hash
algorithms will be reduced over time.
6. Normative References
[COSE] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>.
[FIPS-180-4] [FIPS-180-4]
National Institute of Standards and Technology, "Secure National Institute of Standards and Technology, "Secure
Hash Standard", FIPS PUB 180-4, August 2015. Hash Standard", FIPS PUB 180-4, August 2015.
[I-D.ietf-cose-rfc8152bis-struct] [I-D.ietf-cose-rfc8152bis-struct]
Schaad, J., "CBOR Object Signing and Encryption (COSE) - Schaad, J., "CBOR CBOR Object Signing and Encryption
Structures and Process", draft-ietf-cose-rfc8152bis- (COSE): Structures and Process", draft-ietf-cose-
struct-01 (work in progress), 14 February 2019, rfc8152bis-struct-02 (work in progress), March 11, 2019,
<https://www.ietf.org/archive/id/draft-ietf-cose- <https://www.ietf.org/archive/id/draft-ietf-cose-
rfc8152bis-struct-01>. rfc8152bis-struct-02>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
6. Informative References 7. Informative References
[CMS] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, [CMS] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009, RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>. <https://www.rfc-editor.org/info/rfc5652>.
[ESS] Hoffman, P., Ed., "Enhanced Security Services for S/MIME", [ESS] Hoffman, P., Ed., "Enhanced Security Services for S/MIME",
RFC 2634, DOI 10.17487/RFC2634, June 1999, RFC 2634, DOI 10.17487/RFC2634, June 1999,
<https://www.rfc-editor.org/info/rfc2634>. <https://www.rfc-editor.org/info/rfc2634>.
[I-D.ietf-cose-x509] [I-D.ietf-cose-x509]
skipping to change at line 307 skipping to change at page 10, line 4
[CMS] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, [CMS] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009, RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>. <https://www.rfc-editor.org/info/rfc5652>.
[ESS] Hoffman, P., Ed., "Enhanced Security Services for S/MIME", [ESS] Hoffman, P., Ed., "Enhanced Security Services for S/MIME",
RFC 2634, DOI 10.17487/RFC2634, June 1999, RFC 2634, DOI 10.17487/RFC2634, June 1999,
<https://www.rfc-editor.org/info/rfc2634>. <https://www.rfc-editor.org/info/rfc2634>.
[I-D.ietf-cose-x509] [I-D.ietf-cose-x509]
Schaad, J., "CBOR Object Signing and Encryption (COSE): Schaad, J., "CBOR Object Signing and Encryption (COSE):
Headers for carrying and referencing X.509 certificates", Headers for carrying and referencing X.509 certificates",
draft-ietf-cose-x509-00 (work in progress), 29 January draft-ietf-cose-x509-01 (work in progress), March 11,
2019, 2019,
<https://www.ietf.org/archive/id/draft-ietf-cose-x509-00>. <https://www.ietf.org/archive/id/draft-ietf-cose-x509-01>.
[RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1 [RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1
(SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001, (SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001,
<https://www.rfc-editor.org/info/rfc3174>. <https://www.rfc-editor.org/info/rfc3174>.
[RFC6194] Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security [RFC6194] Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
Considerations for the SHA-0 and SHA-1 Message-Digest Considerations for the SHA-0 and SHA-1 Message-Digest
Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011, Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,
<https://www.rfc-editor.org/info/rfc6194>. <https://www.rfc-editor.org/info/rfc6194>.
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