draft-ietf-cose-hash-algs-03.txt   draft-ietf-cose-hash-algs-04.txt 
Network Working Group J. Schaad Network Working Group J. Schaad
Internet-Draft August Cellars Internet-Draft August Cellars
Intended status: Informational 9 March 2020 Intended status: Informational 29 May 2020
Expires: 10 September 2020 Expires: 30 November 2020
CBOR Object Signing and Encryption (COSE): Hash Algorithms CBOR Object Signing and Encryption (COSE): Hash Algorithms
draft-ietf-cose-hash-algs-03 draft-ietf-cose-hash-algs-04
Abstract Abstract
The CBOR Object Signing and Encryption (COSE) syntax The CBOR Object Signing and Encryption (COSE) syntax
[I-D.ietf-cose-rfc8152bis-struct] does not define any direct methods [I-D.ietf-cose-rfc8152bis-struct] does not define any direct methods
for using hash algorithms. There are however circumstances where for using hash algorithms. There are however circumstances where
hash algorithms are used: Indirect signatures where the hash of one hash algorithms are used, such as indirect signatures where the hash
or more contents are signed. X.509 certificate or other object of one or more contents are signed, and X.509 certificate or other
identification by the use of a fingerprint. This document defines a object identification by the use of a fingerprint. This document
set of hash algorithms that are identified by COSE Algorithm defines a set of hash algorithms that are identified by COSE
Identifiers. Algorithm Identifiers.
Contributing to this document Contributing to this document
This note is to be removed before publishing as an RFC. This note is to be removed before publishing as an RFC.
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 https://github.com/ changes should be submitted as pull requests at https://github.com/
cose-wg/X509 Editorial changes can be managed in GitHub, but any cose-wg/X509 Editorial changes can be managed in GitHub, but any
substantial issues need to be discussed on the COSE mailing list. substantial issues need to be discussed on the COSE mailing list.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 10 September 2020. This Internet-Draft will expire on 30 November 2020.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
skipping to change at page 2, line 28 skipping to change at page 2, line 28
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Terminology . . . . . . . . . . . . . . . . 3 1.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
2. Hash Algorithm Usage . . . . . . . . . . . . . . . . . . . . 3 2. Hash Algorithm Usage . . . . . . . . . . . . . . . . . . . . 3
2.1. Example CBOR hash structure . . . . . . . . . . . . . . . 4 2.1. Example CBOR hash structure . . . . . . . . . . . . . . . 4
3. Hash Algorithm Identifiers . . . . . . . . . . . . . . . . . 5 3. Hash Algorithm Identifiers . . . . . . . . . . . . . . . . . 5
3.1. SHA-1 Hash Algorithm . . . . . . . . . . . . . . . . . . 5 3.1. SHA-1 Hash Algorithm . . . . . . . . . . . . . . . . . . 5
3.2. SHA-2 Hash Algorithms . . . . . . . . . . . . . . . . . . 6 3.2. SHA-2 Hash Algorithms . . . . . . . . . . . . . . . . . . 6
3.3. SHAKE Algorithms . . . . . . . . . . . . . . . . . . . . 7 3.3. SHAKE Algorithms . . . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4.1. COSE Algorithm Registry . . . . . . . . . . . . . . . . . 8 4.1. COSE Algorithm Registry . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. Normative References . . . . . . . . . . . . . . . . . . . . 9 6. Normative References . . . . . . . . . . . . . . . . . . . . 9
7. Informative References . . . . . . . . . . . . . . . . . . . 10 7. Informative References . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11
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
just 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. Additionally, an itself provide any strong security service. Additionally, an
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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.
2. Hash Algorithm Usage 2. Hash Algorithm Usage
As noted in the previous section, hash functions can be used for a As noted in the previous section, hash functions can be used for a
variety of purposes. Some of these purposes require that a hash variety of purposes. Some of these purposes require that a hash
function be cryptographically strong, these include direct and function be cryptographically strong. These include direct and
indirect signatures. That is, using the hash as part of the 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 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. uses of hash functions do not require the same level of strength.
This document contains some hash functions that are not designed to This document contains some hash functions that are not designed to
be used for cryptographic operations. An application that is using a be used for cryptographic operations. An application that is using a
hash function needs to carefully evaluate exactly what hash hash function needs to carefully evaluate exactly what hash
properties are needed and which hash functions are going to provide properties are needed and which hash functions are going to provide
them. Applications should also make sure that the ability to change them. Applications should also make sure that the ability to change
hash functions is part of the base design as cryptographic advances hash functions is part of the base design as cryptographic advances
are sure to reduce the strength of a hash function. are sure to reduce the strength of a hash function.
A hash function is a map from one, normally large, bit string to a A hash function is a map from one, normally large, bit string to a
second, usually smaller, bit string. There are going to be second, usually smaller, bit string. There are going to be
collisions by a hash function, the trick is to make sure that it is 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 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 value. The standard "Collision Attack" is one where an attacker can
find two different messages that have the same hash value. If a find two different messages that have the same hash value. If a
collision attack exists, then the function SHOULD NOT be used for a collision attack exists, then the function SHOULD NOT be used for a
cryptographic purpose. The only reason why such a hash function is cryptographic purpose. The only reason why such a hash function is
used is when there is absolutely no other choice (e.g. a Hardware used is when there is absolutely no other choice (e.g. a Hardware
Security Module (HSM) that cannot be replaced), and only after Security Module (HSM) that cannot be replaced), and only after
looking at the possible security issues. Cryptographic purposes looking at the possible security issues. Cryptographic purposes
would include the creation of signatures or the use of hashes for would include the creation of signatures or the use of hashes for
indirect signatures. These functions may still be usable for non- indirect signatures. These functions may still be usable for non-
skipping to change at page 4, line 46 skipping to change at page 4, line 46
[COSE] did not provide a default structure for holding a hash value [COSE] did not provide a default structure for holding a hash value
not only because no separate hash algorithms were defined, but not only because no separate hash algorithms were defined, but
because how the structure is setup is frequently application because how the structure is setup is frequently application
specific. There are four fields that are often included as part of a specific. There are four fields that are often included as part of a
hash structure: hash structure:
* The hash algorithm identifier. * The hash algorithm identifier.
* The hash value. * The hash value.
* A pointer to the value that was hashed, this could be a pointer to * A pointer to the value that was hashed. this could be a pointer
a file, an object that can be obtained from the network, or a to a file, an object that can be obtained from the network, or a
pointer to someplace in the message, or something very application pointer to someplace in the message, or something very application
specific. specific.
* Additional data, this can be something as simple as a random value * Additional data, this can be something as simple as a random value
to make finding hash collisions slightly harder (as the value to make finding hash collisions slightly harder (as the value
handed to the application cannot have been selected to have a handed to the application cannot have been selected to have a
collision), or as complicated as a set of processing instructions collision), or as complicated as a set of processing instructions
that are used with the object that is pointed to. The additional that are used with the object that is pointed to. The additional
data can be dealt with in a number of ways, prepending or data can be dealt with in a number of ways, prepending or
appending to the content, but it is strongly suggested to it appending to the content, but it is strongly suggested to it
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An example of a structure which permits all of the above fields to An example of a structure which permits all of the above fields to
exist would look like the following. exist would look like the following.
COSE_Hash_V = ( COSE_Hash_V = (
1 : int / tstr, # Algorithm identifier 1 : int / tstr, # Algorithm identifier
2 : bstr, # Hash value 2 : bstr, # Hash value
3 : tstr ?, # Location of object hashed 3 : tstr ?, # Location of object hashed
4 : any ? # object containing other details and things 4 : any ? # object containing other details and things
) )
An alternate structure that could be used for situations where one is An alternative structure that could be used for situations where one
searching a group of objects for a match. In this case, the location is searching a group of objects for a match. In this case, the
would not be needed and adding extra data to the hash would be location would not be needed and adding extra data to the hash would
counterproductive. This results in a structure that looks like this: be counterproductive. This results in a structure that looks like
this:
COSE_Hash_Find = [ COSE_Hash_Find = [
hashAlg : int / tstr, hashAlg : int / tstr,
hashValue : bstr hashValue : bstr
] ]
3. Hash Algorithm Identifiers 3. Hash Algorithm Identifiers
3.1. SHA-1 Hash Algorithm 3.1. SHA-1 Hash Algorithm
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and some of the trade-offs involved. and some of the trade-offs involved.
* *SHA-256/64* provides a truncated hash. The length of the * *SHA-256/64* provides a truncated hash. The length of the
truncation is designed to allow for smaller transmission size. truncation is designed to allow for smaller transmission size.
The trade-off is that the odds that a collision will occur The trade-off is that the odds that a collision will occur
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
used to select possible certificates and, if there are multiple is 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 an efficient hash algorithm for 32-bit currently. SHA-256 is an efficient hash algorithm for 32-bit
hardware. hardware.
* *SHA-384* and *SHA-512* hash functions are efficient for 64-bit * *SHA-384* and *SHA-512* hash functions are efficient for 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.
The COSE capabilities for these algorithms is an empty array. The COSE capabilities array for these algorithms is empty.
+-----------+-----+-----------+--------------+---------+------------+ +-----------+-----+-----------+--------------+---------+------------+
| Name |Value|Description| Capabilities |Reference|Recommended | | Name |Value|Description| Capabilities |Reference|Recommended |
+===========+=====+===========+==============+=========+============+ +===========+=====+===========+==============+=========+============+
|SHA-256/64 |TBD1 | SHA-2 | [] | [This |Filter Only | |SHA-256/64 |TBD1 | SHA-2 | [] | [This |Filter Only |
| | | 256-bit | |Document]| | | | | 256-bit | |Document]| |
| | | Hash | | | | | | | Hash | | | |
| | | truncated | | | | | | | truncated | | | |
| | |to 64-bits | | | | | | |to 64-bits | | | |
+-----------+-----+-----------+--------------+---------+------------+ +-----------+-----+-----------+--------------+---------+------------+
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| | | 512-bit | |Document]| | | | | 512-bit | |Document]| |
| | | Hash | | | | | | | Hash | | | |
| | | truncated | | | | | | | truncated | | | |
| | |to 256-bits| | | | | | |to 256-bits| | | |
+-----------+-----+-----------+--------------+---------+------------+ +-----------+-----+-----------+--------------+---------+------------+
Table 2: SHA-2 Hash Algorithms Table 2: SHA-2 Hash Algorithms
3.3. SHAKE Algorithms 3.3. SHAKE Algorithms
The family SHA-3 hash algorithms [FIPS-202] was the result of a The family of SHA-3 hash algorithms [FIPS-202] 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-2 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 shorter SHAKE hash value, the differences is that when computing a shorter SHAKE hash value, the
value is not a prefix of the result of computing the longer hash. value is not a prefix of the result of computing the longer hash.
Unlike the SHA-2 hash functions, no algorithm identifier is created Unlike the SHA-2 hash functions, no algorithm identifier is created
for shorter lengths. Applications can specify a minimum length for for shorter lengths. Applications can specify a minimum length for
any hash function. A validator can infer the actual length from the any hash function. A validator can infer the actual length from the
hash value in these cases. hash value in these cases.
The COSE capabilities for these algorithms is an empty array. The COSE capabilities array for these algorithms is empty.
+--------+-----+-------------+--------------+---------+-------------+ +--------+-----+-------------+--------------+---------+-------------+
| Name |Value| Description | Capabilities |Reference| Recommended | | Name |Value| Description | Capabilities |Reference| Recommended |
+========+=====+=============+==============+=========+=============+ +========+=====+=============+==============+=========+=============+
|SHAKE128|TBD10|128-bit SHAKE| [] | [This | Yes | |SHAKE128|TBD10|128-bit SHAKE| [] | [This | Yes |
| | | | |Document]| | | | | | |Document]| |
+--------+-----+-------------+--------------+---------+-------------+ +--------+-----+-------------+--------------+---------+-------------+
|SHAKE256|TBD11|256-bit SHAKE| [] | [This | Yes | |SHAKE256|TBD11|256-bit SHAKE| [] | [This | Yes |
| | | | |Document]| | | | | | |Document]| |
+--------+-----+-------------+--------------+---------+-------------+ +--------+-----+-------------+--------------+---------+-------------+
Table 3: SHAKE Hash Functions Table 3: SHAKE Hash Functions
4. IANA Considerations 4. IANA Considerations
The IANA actions in [I-D.ietf-cose-rfc8152bis-struct] and
[I-D.ietf-cose-rfc8152bis-algs] need to be executed before the
actions in this document. Where early allocation of data points has
been made, these should be preseved.
4.1. 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.
In addition, IANA is to add the value of 'Filter Only' to the set of 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 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 used for hash functions and indicates that it is not to be used for
purposes which require collision resistance. purposes which require collision resistance. IANA is requested to
add this document to the reference section for this table due to this
addition.
5. Security Considerations 5. Security Considerations
The security considerations have already been called out as part of Protocols need to perform a careful analysis of the properties of a
the previous text. The following issues need to be dealt with: hash function that are needed and how they map onto the possible
attacks. In particular, one needs to distinguish between those uses
* Protocols need to perform a careful analysis of the properties of that need the cryptographic properties, i.e. collision resistance,
a hash function that are needed and how they map onto the possible and properties that correspond to possible object identification.
attacks. In particular, one needs to distinguish between those The different attacks correspond to who or what is being protected:
uses that need the cryptographic properties, i.e. collision is it the originator that is the attacker or a third party? This is
resistance, and properties that correspond to possible object the difference between collision resistance and second pre-image
identification. The different attacks correspond to who or what resistance. As a general rule, longer hash values are "better" than
is being protected, is it the originator that is the attacker or a short ones, but trade-offs of transmission size, timeliness, and
third party? This is the difference between collision resistance security all need to be included as part of this analysis. In many
and second pre-image resistance. As a general rule, longer hash cases the value being hashed is a public value, as such pre-image
values are "better" than short ones, but trade-offs of resistance is not part of this analysis.
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 Algorithm agility needs to be considered a requirement for any use of
of hash functions. As with any cryptographic function, hash hash functions. As with any cryptographic function, hash functions
functions are under constant attack and the strength of hash are under constant attack and the strength of hash algorithms will be
algorithms will be reduced over time. reduced over time.
6. Normative References 6. Normative References
[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>.
[I-D.ietf-cose-rfc8152bis-struct] [I-D.ietf-cose-rfc8152bis-struct]
Schaad, J., "CBOR Object Signing and Encryption (COSE): Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", Work in Progress, Internet-Draft, Structures and Process", Work in Progress, Internet-Draft,
draft-ietf-cose-rfc8152bis-struct-07, 17 November 2019, draft-ietf-cose-rfc8152bis-struct-09, 14 May 2020,
<https://tools.ietf.org/html/draft-ietf-cose-rfc8152bis- <https://tools.ietf.org/html/draft-ietf-cose-rfc8152bis-
struct-07>. struct-09>.
[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.
[FIPS-202] National Institute of Standards and Technology, "SHA-3 [FIPS-202] National Institute of Standards and Technology, "SHA-3
Standard: Permutation-Based Hash and Extendable-Output Standard: Permutation-Based Hash and Extendable-Output
Functions", FIPS PUB 202, August 2015. Functions", FIPS PUB 202, August 2015.
[COSE] Schaad, J., "CBOR Object Signing and Encryption (COSE)", [COSE] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
skipping to change at page 10, line 19 skipping to change at page 10, line 36
[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", Header parameters for carrying and referencing X.509
Work in Progress, Internet-Draft, draft-ietf-cose-x509-05, certificates", Work in Progress, Internet-Draft, draft-
4 November 2019, ietf-cose-x509-06, 9 March 2020,
<https://tools.ietf.org/html/draft-ietf-cose-x509-05>. <https://tools.ietf.org/html/draft-ietf-cose-x509-06>.
[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>.
[I-D.ietf-cose-rfc8152bis-algs]
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", Work in Progress, Internet-Draft,
draft-ietf-cose-rfc8152bis-algs-08, 14 May 2020,
<https://tools.ietf.org/html/draft-ietf-cose-rfc8152bis-
algs-08>.
[SHA-1-collision] [SHA-1-collision]
Stevens, M., Bursztein, E., Karpman, P., Albertini, A., Stevens, M., Bursztein, E., Karpman, P., Albertini, A.,
and Y. Markov, "The first collision for full SHA-1", and Y. Markov, "The first collision for full SHA-1",
February 2017, February 2017,
<https://shattered.io/static/shattered.pdf>. <https://shattered.io/static/shattered.pdf>.
Author's Address Author's Address
Jim Schaad Jim Schaad
August Cellars August Cellars
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