draft-ietf-cose-hash-algs-04.txt   draft-ietf-cose-hash-algs-05.txt 
Network Working Group J. Schaad Network Working Group J. Schaad
Internet-Draft August Cellars Internet-Draft August Cellars
Intended status: Informational 29 May 2020 Intended status: Informational 6 July 2020
Expires: 30 November 2020 Expires: 7 January 2021
CBOR Object Signing and Encryption (COSE): Hash Algorithms CBOR Object Signing and Encryption (COSE): Hash Algorithms
draft-ietf-cose-hash-algs-04 draft-ietf-cose-hash-algs-05
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, such as indirect signatures where the hash hash algorithms are used, such as indirect signatures where the hash
of one or more contents are signed, and X.509 certificate or other of one or more contents are signed, and X.509 certificate or other
object identification by the use of a fingerprint. This document object identification by the use of a fingerprint. This document
defines a set of hash algorithms that are identified by COSE defines a set of hash algorithms that are identified by COSE
Algorithm 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.
skipping to change at page 1, line 46 skipping to change at page 1, line 46
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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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 30 November 2020. This Internet-Draft will expire on 7 January 2021.
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 26 skipping to change at page 2, line 26
as described in Section 4.e of the Trust Legal Provisions and are as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License. provided without warranty as described in the Simplified BSD License.
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 . . . . . . . . . . . . . . . . . . 6
3.2. SHA-2 Hash Algorithms . . . . . . . . . . . . . . . . . . 6 3.2. SHA-2 Hash Algorithms . . . . . . . . . . . . . . . . . . 6
3.3. SHAKE Algorithms . . . . . . . . . . . . . . . . . . . . 8 3.3. SHAKE Algorithms . . . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
4.1. COSE Algorithm Registry . . . . . . . . . . . . . . . . . 8 4.1. COSE Algorithm Registry . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. Normative References . . . . . . . . . . . . . . . . . . . . 9 6. Normative References . . . . . . . . . . . . . . . . . . . . 10
7. Informative References . . . . . . . . . . . . . . . . . . . 10 7. Informative References . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
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,
itself provide any strong security service. Additionally, an by 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 include any additional data that needs to be hashed, so that it can include any additional data that needs to be hashed,
as well as methods of obtaining the data. 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.
Indirect signing of content is a paradigm where the content is not Indirect signing of content is a paradigm where the content is not
directly signed, but instead a hash of the content is computed and directly signed, but instead a hash of the content is computed and
that hash value, along with the hash algorithm, is included in the that hash value, along with an identifier for the hash algorithm, is
content that will be signed. Doing indirect signing allows for a included in the content that will be signed. Doing indirect signing
signature to be validated without first downloading all of the allows for a signature to be validated without first downloading all
content associated with the signature. This capability can be of of the content associated with the signature. Rather the signature
even greater importance in a constrained environment as not all of can be validated on all of the hash values and pointers to the
the content signed may be needed by the device. associated contents, then those associated parts can be downloaded,
the hash value of that part computed, and then compared to the hash
value in the signed content. This capability can be of even greater
importance in a constrained environment as not all of the content
signed may be needed by the device. An example of how this is used
can be found in [I-D.ietf-suit-manifest].
The use of hashes to identify objects is something that has been very The use of hashes to identify objects is something that has been very
common. One of the primary things that has been identified by a hash common. One of the primary things that has been identified by a hash
function for secure message is a certificate. Two examples of this function in a secure message is a certificate. Two examples of this
can be found in [ESS] and the newly defined COSE equivalents in can be found in [ESS] and the COSE equivalents in
[I-D.ietf-cose-x509]. [I-D.ietf-cose-x509].
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.
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 may 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 [BCP201].
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. As the number of possible input
collisions by a hash function. The trick is to make sure that it is values is far greater than the number of possible output values, it
difficult to find two values that are going to map to the same output is inevitable that there are going to be collisions. The trick is to
value. The standard "Collision Attack" is one where an attacker can make sure that it is difficult to find two values that are going to
find two different messages that have the same hash value. If a map to the same output value. A "Collision Attack" is one where an
collision attack exists, then the function SHOULD NOT be used for a attacker can find two different messages that have the same hash
cryptographic purpose. The only reason why such a hash function is value. A hash function that is susceptible to practical collision
used is when there is absolutely no other choice (e.g. a Hardware attacks, SHOULD NOT be used for a cryptographic purpose. The
Security Module (HSM) that cannot be replaced), and only after discovery of theoretical collision attacks against a given hash
looking at the possible security issues. Cryptographic purposes function SHOULD trigger a review of the continued suitability of the
would include the creation of signatures or the use of hashes for algorithm if alternatives are available and migration is viable. The
indirect signatures. These functions may still be usable for non- only reason why such a hash function is used is when there is
cryptographic purposes. absolutely no other choice (e.g. a Hardware Security Module (HSM)
that cannot be replaced), and only after looking at the possible
security issues. Cryptographic purposes would include the creation
of signatures or the use of hashes for indirect signatures. These
functions may still be usable for non-cryptographic purposes.
An example of a non-cryptographic use of a hash is for filtering from An example of a non-cryptographic use of a hash is for filtering from
a collection of values to find possible candidates that can later be a collection of values to find a set of possible candidates, the
checked to see if they are the correct one. A simple example of this candidates can then be check to see if they can successfully be used.
is the classic fingerprint of a certificate. If the fingerprint is A simple example of this is the classic fingerprint of a certificate.
used to verify that it is the correct certificate, then that usage is If the fingerprint is used to verify that it is the correct
subject to a collision attack as above. If however, the fingerprint certificate, then that usage is a cryptographic one and is subject to
is used to sort through a collection of certificates to find those the warning above about collision attack. If, however, the
that might be used for the purpose of verifying a signature, a simple fingerprint is used to sort through a collection of certificates to
filter capability is sufficient. In this case, one still needs to find those that might be used for the purpose of verifying a
validate that the public key validates the signature (and the signature, a simple filter capability is sufficient. In this case,
certificate is trusted), and all certificates that don't contain a one still needs to confirm that the public key validates the
key that validates the signature can be discarded as false positives. 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 To distinguish between these two cases, a new value in the
recommended column of the COSE Algorithms registry is to be added. recommended column of the COSE Algorithms registry is to be added.
"Filter Only" indicates that the only purpose of a hash function "Filter Only" indicates that the only purpose of a hash function
should be to filter results and not those which require collision should be to filter results and it is not intended for applications
resistance. which require a cryptographically strong algorithm.
2.1. Example CBOR hash structure 2.1. Example CBOR hash structure
[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 * 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 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 (i.e. salt) to make finding hash collisions slightly harder (as
handed to the application cannot have been selected to have a the payload handed to the application could have been selected to
collision), or as complicated as a set of processing instructions have a collision), or as complicated as a set of processing
that are used with the object that is pointed to. The additional instructions that are used with the object that is pointed to.
data can be dealt with in a number of ways, prepending or The additional data can be dealt with in a number of ways,
appending to the content, but it is strongly suggested to it prepending or appending to the content, but it is strongly
either be a fixed known size, or the lengths of the pieces being suggested that it either be a fixed known size, or the lengths of
hashed be included. (Encoding as a CBOR array accomplished this the pieces being hashed be included. (Encoding as a CBOR array
requirement.) accomplishes this requirement.)
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 that was hashed
4 : any ? # object containing other details and things ? 4 : any # object containing other details and things
) )
An alternative structure that could be used for situations where one Below is an alternative structure that could be used in situations
is searching a group of objects for a match. In this case, the where one is searching a group of objects for a matching hash value.
location would not be needed and adding extra data to the hash would In this case, the location would not be needed and adding extra data
be counterproductive. This results in a structure that looks like to the hash would be counterproductive. This results in a structure
this: 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
The SHA-1 hash algorithm [RFC3174] was designed by the United States The SHA-1 hash algorithm [RFC3174] was designed by the United States
National Security Agency and published in 1995. Since that time a 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].
Despite 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
skipping to change at page 6, line 6 skipping to change at page 6, line 14
3.1. SHA-1 Hash Algorithm 3.1. SHA-1 Hash Algorithm
The SHA-1 hash algorithm [RFC3174] was designed by the United States The SHA-1 hash algorithm [RFC3174] was designed by the United States
National Security Agency and published in 1995. Since that time a 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].
Despite 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 codepoint for the use of
hash algorithm. Some of these situations are with historic HSMs this 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, other situations are where the SHA-1
the purpose of filtering and thus the collision resistance property value is used for the purpose of filtering and thus the collision
is not needed. resistance property 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 it should no
longer be used, the algorithm will be registered with the longer be used, the algorithm will be registered with the
recommendation of "Filter Only". recommendation of "Filter Only". This provides guidance about when
the algorithm is safe for use, while discouraging usage where it is
not safe.
The COSE capabilities for this algorithm is an empty array. The COSE capabilities for these algorithms is an empty array.
+-----+------+-------------+--------------+-----------+-------------+ +=====+======+=============+==============+===========+=============+
|Name |Value | Description | Capabilities | Reference | Recommended | |Name |Value | Description | Capabilities | Reference | Recommended |
+=====+======+=============+==============+===========+=============+ +=====+======+=============+==============+===========+=============+
|SHA-1| TBD6 | SHA-1 Hash | [] | [This | Filter Only | |SHA-1| TBD6 | SHA-1 Hash | [] | [This | Filter Only |
| | | | | Document] | | | | | | | Document] | |
+-----+------+-------------+--------------+-----------+-------------+ +-----+------+-------------+--------------+-----------+-------------+
Table 1: SHA-1 Hash Algorithm Table 1: SHA-1 Hash Algorithm
3.2. SHA-2 Hash Algorithms 3.2. SHA-2 Hash Algorithms
skipping to change at page 6, line 44 skipping to change at page 7, line 8
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
inclusion in this document are based on those different parameters inclusion in this document are based on those different parameters
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. Use of this hash function needs analyze
need either to analysis the potential problems with having a of the potential problems with having a collision occur, or must
collision occur, or where the only function of the hash is to be limited to where the function of the hash is non-cryptographic.
narrow the possible choices.
The latter is the case for [I-D.ietf-cose-x509]. The hash value 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 is used to select possible certificates and, if there are multiple
choices then, each choice can be tested by using the public key. choices remaining 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 array for these algorithms is empty. 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 | | | |
+-----------+-----+-----------+--------------+---------+------------+ +-----------+-----+-----------+--------------+---------+------------+
| SHA-256 |TBD2 | SHA-2 | [] | [This | Yes | | SHA-256 |TBD2 | SHA-2 | [] | [This | Yes |
| | | 256-bit | |Document]| | | | | 256-bit | |Document]| |
skipping to change at page 8, line 10 skipping to change at page 8, line 40
| | |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 of 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. This is the reason for including these
algorithms in this document.
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 difference 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. The length of the hash value stored is 128-bits
any hash function. A validator can infer the actual length from the for SHAKE-128 and 256-bits for SHAKE-256.
hash value in these cases.
The COSE capabilities array for these algorithms is empty. 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 | [] | [This | Yes |
| | | | |Document]| | | | | SHAKE-128 | |Document]| |
+--------+-----+-------------+--------------+---------+-------------+ +--------+-----+-------------+--------------+---------+-------------+
|SHAKE256|TBD11|256-bit SHAKE| [] | [This | Yes | |SHAKE256|TBD11| 256-bit | [] | [This | Yes |
| | | | |Document]| | | | | SHAKE-256 | |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 The IANA actions in [I-D.ietf-cose-rfc8152bis-struct] and
[I-D.ietf-cose-rfc8152bis-algs] need to be executed before the [I-D.ietf-cose-rfc8152bis-algs] need to be executed before the
actions in this document. Where early allocation of data points has actions in this document. Where early allocation of codepoints has
been made, these should be preseved. been made, these should be preserved.
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.
skipping to change at page 9, line 22 skipping to change at page 10, line 10
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. IANA is requested to purposes which require collision resistance. IANA is requested to
add this document to the reference section for this table due to this add this document to the reference section for this table due to this
addition. addition.
5. Security Considerations 5. Security Considerations
Protocols need to perform a careful analysis of the properties of a Protocols need to perform a careful analysis of the properties of a
hash function that are needed and how they map onto the possible hash function that are needed and how they map onto the possible
attacks. In particular, one needs to distinguish between those uses attacks. In particular, one needs to distinguish between those uses
that need the cryptographic properties, i.e. collision resistance, that need the cryptographic properties, such as collision resistance,
and properties that correspond to possible object identification. and properties that correspond to possible object identification.
The different attacks correspond to who or what is being protected: 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 is it the originator that is the attacker or a third party? This is
the difference between collision resistance and second pre-image the difference between collision resistance and second pre-image
resistance. As a general rule, longer hash values are "better" than resistance. As a general rule, longer hash values are "better" than
short ones, but trade-offs of transmission size, timeliness, and short ones, but trade-offs of transmission size, timeliness, and
security all need to be included as part of this analysis. In many 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 cases the value being hashed is a public value and, as such, pre-
resistance is not part of this analysis. image resistance is not part of this analysis.
Algorithm agility needs to be considered a requirement for any use of Algorithm agility needs to be considered a requirement for any use of
hash functions. As with any cryptographic function, hash functions hash functions [BCP201]. As with any cryptographic function, hash
are under constant attack and the strength of hash algorithms will be functions are under constant attack and the cryptographic strength of
reduced over time. hash algorithms will be 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-09, 14 May 2020, draft-ietf-cose-rfc8152bis-struct-10, 2 June 2020,
<https://tools.ietf.org/html/draft-ietf-cose-rfc8152bis- <https://tools.ietf.org/html/draft-ietf-cose-rfc8152bis-
struct-09>. struct-10>.
[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)", [RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1
RFC 8152, DOI 10.17487/RFC8152, July 2017, (SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001,
<https://www.rfc-editor.org/info/rfc8152>. <https://www.rfc-editor.org/info/rfc3174>.
7. 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]
Schaad, J., "CBOR Object Signing and Encryption (COSE): Schaad, J., "CBOR Object Signing and Encryption (COSE):
Header parameters for carrying and referencing X.509 Header parameters for carrying and referencing X.509
certificates", Work in Progress, Internet-Draft, draft- certificates", Work in Progress, Internet-Draft, draft-
ietf-cose-x509-06, 9 March 2020, ietf-cose-x509-06, 9 March 2020,
<https://tools.ietf.org/html/draft-ietf-cose-x509-06>. <https://tools.ietf.org/html/draft-ietf-cose-x509-06>.
[RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1
(SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001,
<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] [I-D.ietf-cose-rfc8152bis-algs]
Schaad, J., "CBOR Object Signing and Encryption (COSE): Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", Work in Progress, Internet-Draft, Initial Algorithms", Work in Progress, Internet-Draft,
draft-ietf-cose-rfc8152bis-algs-08, 14 May 2020, draft-ietf-cose-rfc8152bis-algs-10, 26 June 2020,
<https://tools.ietf.org/html/draft-ietf-cose-rfc8152bis- <https://tools.ietf.org/html/draft-ietf-cose-rfc8152bis-
algs-08>. algs-10>.
[I-D.ietf-suit-manifest]
Moran, B., Tschofenig, H., Birkholz, H., and K. Zandberg,
"A Concise Binary Object Representation (CBOR)-based
Serialization Format for the Software Updates for Internet
of Things (SUIT) Manifest", Work in Progress, Internet-
Draft, draft-ietf-suit-manifest-07, 9 June 2020,
<https://tools.ietf.org/html/draft-ietf-suit-manifest-07>.
[BCP201] Housley, R., "Guidelines for Cryptographic Algorithm
Agility and Selecting Mandatory-to-Implement Algorithms",
BCP 201, RFC 7696, November 2015.
<https://www.rfc-editor.org/info/bcp201>
[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>.
[COSE] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>.
Author's Address Author's Address
Jim Schaad Jim Schaad
August Cellars August Cellars
Email: ietf@augustcellars.com Email: ietf@augustcellars.com
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