rfc9054.original.xml		rfc9054.xml
	<?xml version='1.0' encoding='utf-8'?>		<?xml version='1.0' encoding='utf-8'?>
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	<?rfc toc="yes"?>		ensus="true" docName="draft-ietf-cose-hash-algs-09" indexInclude="true" ipr="tru
	<?rfc symrefs="yes"?>		st200902" number="9054" prepTime="2022-08-24T14:59:32" scripts="Common,Latin" so
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	<rfc ipr="trust200902" docName="draft-ietf-cose-hash-algs-09" category="info" ve		<link href="https://datatracker.ietf.org/doc/draft-ietf-cose-hash-algs-09" rel
	rsion="3" submissionType="IETF">		="prev"/>
			<link href="https://dx.doi.org/10.17487/rfc9054" rel="alternate"/>
			<link href="urn:issn:2070-1721" rel="alternate"/>
	<front>		<front>
	<title abbrev="COSE Hashes">CBOR Object Signing and Encryption (COSE): Hash Algorithms</title>		<title abbrev="COSE Hashes">CBOR Object Signing and Encryption (COSE): Hash Algorithms</title>
			<seriesInfo name="RFC" value="9054" stream="IETF"/>
	<author initials="J." surname="Schaad" fullname="Jim Schaad">		<author initials="J." surname="Schaad" fullname="Jim Schaad">
	<organization>August Cellars</organization>		<organization showOnFrontPage="true">August Cellars</organization>
	<address>		<address/>
	<email>ietf@augustcellars.com</email>
	</address>
	</author>		</author>
	<date/>		<date month="08" year="2022"/>
	<area>Security</area>		<area>Security</area>
	<abstract>		<workgroup>COSE Working Group</workgroup>
	<t>		<keyword>SHA-1 Hash Algorithm</keyword>
	The CBOR Object Signing and Encryption (COSE) syntax <xref target="I-D.i		<keyword>SHA-2 HAsh Algorithm</keyword>
	etf-cose-rfc8152bis-struct"/> does not define any direct methods for using hash		<keyword>SHAKE Algorithm</keyword>
	algorithms.		<abstract pn="section-abstract">
	There are, however, circumstances where hash algorithms are used, such a		<t indent="0" pn="section-abstract-1">
	s indirect signatures where the hash of one or more contents are signed, and X.5		The CBOR Object Signing and
	09 certificate or other object identification by the use of a fingerprint.		Encryption (COSE) syntax (see RFC 9052) does not define any
	This document defines a set of hash algorithms that are identified by CO		direct methods for using hash algorithms.
	SE Algorithm Identifiers.		There are, however, circumstances where hash algorithms are used, such
			as indirect signatures, where the hash of one or more contents are
			signed, and identification of an X.509 certificate or other object by the
			use of a fingerprint.
			This document defines hash algorithms that are identified by COSE algori
			thm identifiers.
	</t>		</t>
	</abstract>		</abstract>
	<note removeInRFC="true">		<boilerplate>
	<name>Contributing to this document</name>		<section anchor="status-of-memo" numbered="false" removeInRFC="false" toc=
	<!-- RFC EDITOR - Please remove this note before publishing -->		"exclude" pn="section-boilerplate.1">
	<t>		<name slugifiedName="name-status-of-this-memo">Status of This Memo</name
	The source for this draft is being maintained in GitHub.		>
	Suggested changes should be submitted as pull requests at <eref target="		<t indent="0" pn="section-boilerplate.1-1">
	https://github.com/cose-wg/X509"/>		This document is not an Internet Standards Track specification; it i
	Editorial changes can be managed in GitHub, but any substantial issues n		s
	eed to be discussed on the COSE mailing list.		published for informational purposes.
	</t>		</t>
	</note>		<t indent="0" pn="section-boilerplate.1-2">
			This document is a product of the Internet Engineering Task Force
			(IETF). It represents the consensus of the IETF community. It has
			received public review and has been approved for publication by the
			Internet Engineering Steering Group (IESG). Not all documents
			approved by the IESG are candidates for any level of Internet
			Standard; see Section 2 of RFC 7841.
			</t>
			<t indent="0" pn="section-boilerplate.1-3">
			Information about the current status of this document, any
			errata, and how to provide feedback on it may be obtained at
			<eref target="https://www.rfc-editor.org/info/rfc9054" brackets="non
			e"/>.
			</t>
			</section>
			<section anchor="copyright" numbered="false" removeInRFC="false" toc="excl
			ude" pn="section-boilerplate.2">
			<name slugifiedName="name-copyright-notice">Copyright Notice</name>
			<t indent="0" pn="section-boilerplate.2-1">
			Copyright (c) 2022 IETF Trust and the persons identified as the
			document authors. All rights reserved.
			</t>
			<t indent="0" pn="section-boilerplate.2-2">
			This document is subject to BCP 78 and the IETF Trust's Legal
			Provisions Relating to IETF Documents
			(<eref target="https://trustee.ietf.org/license-info" brackets="none
			"/>) in effect on the date of
			publication of this document. Please review these documents
			carefully, as they describe your rights and restrictions with
			respect to this document. Code Components extracted from this
			document must include Revised BSD License text as described in
			Section 4.e of the Trust Legal Provisions and are provided without
			warranty as described in the Revised BSD License.
			</t>
			</section>
			</boilerplate>
			<toc>
			<section anchor="toc" numbered="false" removeInRFC="false" toc="exclude" p
			n="section-toc.1">
			<name slugifiedName="name-table-of-contents">Table of Contents</name>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="section-to
			c.1-1">
			<li pn="section-toc.1-1.1">
			<t indent="0" keepWithNext="true" pn="section-toc.1-1.1.1"><xref der
			ivedContent="1" format="counter" sectionFormat="of" target="section-1"/>.  <xref
			derivedContent="" format="title" sectionFormat="of" target="name-introduction">
			Introduction</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.1.2">
			<li pn="section-toc.1-1.1.2.1">
			<t indent="0" keepWithNext="true" pn="section-toc.1-1.1.2.1.1"><
			xref derivedContent="1.1" format="counter" sectionFormat="of" target="section-1.
			1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-re
			quirements-terminology">Requirements Terminology</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.2">
			<t indent="0" pn="section-toc.1-1.2.1"><xref derivedContent="2" form
			at="counter" sectionFormat="of" target="section-2"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-hash-algorithm-usage">Hash Algorit
			hm Usage</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.2.2">
			<li pn="section-toc.1-1.2.2.1">
			<t indent="0" keepWithNext="true" pn="section-toc.1-1.2.2.1.1"><
			xref derivedContent="2.1" format="counter" sectionFormat="of" target="section-2.
			1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ex
			ample-cbor-hash-structure">
			Example CBOR Hash Structure
			</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.3">
			<t indent="0" pn="section-toc.1-1.3.1"><xref derivedContent="3" form
			at="counter" sectionFormat="of" target="section-3"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-hash-algorithm-identifiers">Hash A
			lgorithm Identifiers</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.3.2">
			<li pn="section-toc.1-1.3.2.1">
			<t indent="0" pn="section-toc.1-1.3.2.1.1"><xref derivedContent=
			"3.1" format="counter" sectionFormat="of" target="section-3.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-sha-1-hash-algorithm">
			SHA-1 Hash Algorithm</xref></t>
			</li>
			<li pn="section-toc.1-1.3.2.2">
			<t indent="0" pn="section-toc.1-1.3.2.2.1"><xref derivedContent=
			"3.2" format="counter" sectionFormat="of" target="section-3.2"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-sha-2-hash-algorithms"
			>SHA-2 Hash Algorithms</xref></t>
			</li>
			<li pn="section-toc.1-1.3.2.3">
			<t indent="0" pn="section-toc.1-1.3.2.3.1"><xref derivedContent=
			"3.3" format="counter" sectionFormat="of" target="section-3.3"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-shake-algorithms">SHAK
			E Algorithms</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.4">
			<t indent="0" pn="section-toc.1-1.4.1"><xref derivedContent="4" form
			at="counter" sectionFormat="of" target="section-4"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-iana-considerations">IANA Consider
			ations</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.4.2">
			<li pn="section-toc.1-1.4.2.1">
			<t indent="0" pn="section-toc.1-1.4.2.1.1"><xref derivedContent=
			"4.1" format="counter" sectionFormat="of" target="section-4.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-cose-algorithm-registr
			y">COSE Algorithm Registry</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.5">
			<t indent="0" pn="section-toc.1-1.5.1"><xref derivedContent="5" form
			at="counter" sectionFormat="of" target="section-5"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-security-considerations">Security
			Considerations</xref></t>
			</li>
			<li pn="section-toc.1-1.6">
			<t indent="0" pn="section-toc.1-1.6.1"><xref derivedContent="6" form
			at="counter" sectionFormat="of" target="section-6"/>.  <xref derivedContent="" f
			ormat="title" sectionFormat="of" target="name-references">References</xref></t>
			<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
			n-toc.1-1.6.2">
			<li pn="section-toc.1-1.6.2.1">
			<t indent="0" pn="section-toc.1-1.6.2.1.1"><xref derivedContent=
			"6.1" format="counter" sectionFormat="of" target="section-6.1"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-normative-references">
			Normative References</xref></t>
			</li>
			<li pn="section-toc.1-1.6.2.2">
			<t indent="0" pn="section-toc.1-1.6.2.2.1"><xref derivedContent=
			"6.2" format="counter" sectionFormat="of" target="section-6.2"/>.  <xref derived
			Content="" format="title" sectionFormat="of" target="name-informative-references
			">Informative References</xref></t>
			</li>
			</ul>
			</li>
			<li pn="section-toc.1-1.7">
			<t indent="0" pn="section-toc.1-1.7.1"><xref derivedContent="" forma
			t="none" sectionFormat="of" target="section-appendix.a"/><xref derivedContent=""
			format="title" sectionFormat="of" target="name-authors-address">Author's Addres
			s</xref></t>
			</li>
			</ul>
			</section>
			</toc>
	</front>		</front>
	<middle>		<middle>
	<section anchor="introduction">		<section anchor="introduction" numbered="true" removeInRFC="false" toc="incl
	<name>Introduction</name>		ude" pn="section-1">
	<t>		<name slugifiedName="name-introduction">Introduction</name>
	The CBOR Object Signing and Encryption (COSE) syntax does not define any		<t indent="0" pn="section-1-1">
	direct methods for the use of hash algorithms.		The CBOR Object Signing and Encryption (COSE) syntax <xref target="RFC90
	It also does not define a structure syntax that is used to encode a dige		52" format="default" sectionFormat="of" derivedContent="RFC9052"/> does not defi
	sted object structure along the lines of the DigestedData ASN.1 structure in <xr		ne any direct methods for the use of hash algorithms.
	ef target="RFC5652"/>.		It also does not define a structure syntax that is used to encode a dige
			sted object structure along the lines of the DigestedData ASN.1 structure in <xr
			ef target="RFC5652" format="default" sectionFormat="of" derivedContent="CMS"/>.
	This omission was intentional, as a structure consisting of just a diges t identifier, the content, and a digest value does not, by itself, provide any s trong security service.		This omission was intentional, as a structure consisting of just a diges t identifier, the content, and a digest value does not, by itself, provide any s trong security service.
	Additionally, an application is going to be better off defining this typ e of structure so that it can include any additional data that needs to be hashe d, as well as methods of obtaining the data.		Additionally, an application is going to be better off defining this typ e of structure so that it can include any additional data that needs to be hashe d, as well as methods of obtaining the data.
	</t>		</t>
	<t>		<t indent="0" pn="section-1-2">
	While the above is true, there are some cases where having some standard hash algorithms defined for COSE with a common identifier makes a great deal of sense.		While the above is true, there are some cases where having some standard hash algorithms defined for COSE with a common identifier makes a great deal of sense.
	Two of the cases where these are going to be used are:		Two of the cases where these are going to be used are:
	</t>		</t>
	<ul>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-1-3
	<li>		">
			<li pn="section-1-3.1">
	Indirect signing of content, and		Indirect signing of content, and
	</li>		</li>
	<li>		<li pn="section-1-3.2">
	Object identification.		Object identification.
	</li>		</li>
	</ul>		</ul>
	<t>		<t indent="0" pn="section-1-4">
	Indirect signing of content is a paradigm where the content is not direc		Indirect signing of content is a paradigm where the content is not
	tly signed, but instead a hash of the content is computed and that hash value, a		directly signed, but instead a hash of the content is computed, and
	long with an identifier for the hash algorithm, is included in the content that		that hash value -- along with an identifier for the hash algorithm -- is
	will be signed.		included in the content that will be signed.
	Doing indirect signing allows for a signature to be validated without fi		Indirect signing allows for a signature to be validated without first
	rst downloading all of the content associated with the signature.		downloading all of the content associated with the signature.
	Rather the signature can be validated on all of the hash values and poin		Rather, the signature can be validated on all of the hash values and
	ters to the associated contents, then those associated parts can be downloaded,		pointers to the associated contents; those associated parts can then
	the hash value of that part computed, and then compared to the hash value in the		be downloaded, then the hash value of that part can be computed and
	signed content.		compared to the hash value in the signed content.
	This capability can be of even greater importance in a constrained envir		This capability can be of even greater importance in a constrained
	onment as not all of the content signed may be needed by the device.		environment, as not all of the content signed may be needed by the
	An example of how this is used can be found in <xref target="I-D.ietf-su		device. An example of how this is used can be found in <xref target="I-D.
	it-manifest"/>.		ietf-suit-manifest" sectionFormat="of" section="5.4" format="default" derivedLin
			k="https://datatracker.ietf.org/doc/html/draft-ietf-suit-manifest-19#section-5.4
			" derivedContent="SUIT-MANIFEST"/>.
	</t>		</t>
	<t>		<t indent="0" pn="section-1-5">
	The use of hashes to identify objects is something that has been very co mmon.		The use of hashes to identify objects is something that has been very co mmon.
	One of the primary things that has been identified by a hash function in a secure message is a certificate.		One of the primary things that has been identified by a hash function in a secure message is a certificate.
	Two examples of this can be found in <xref target="RFC2634"/> and the CO SE equivalents in <xref target="I-D.ietf-cose-x509"/>.		Two examples of this can be found in <xref target="RFC2634" format="defa ult" sectionFormat="of" derivedContent="ESS"/> and the COSE equivalents in <xref target="I-D.ietf-cose-x509" format="default" sectionFormat="of" derivedContent= "COSE-x509"/>.
	</t>		</t>
	<section anchor="requirements-terminology">		<section anchor="requirements-terminology" numbered="true" removeInRFC="fa
	<name>Requirements Terminology</name>		lse" toc="include" pn="section-1.1">
	<t>		<name slugifiedName="name-requirements-terminology">Requirements Termino
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "S		logy</name>
	HOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in		<t indent="0" pn="section-1.1-1">
	this document are to be interpreted as described in BCP 14 <xref target="RFC211		The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQU
	9"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals,		IRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOUL
	as shown here.		D</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>N
			OT RECOMMENDED</bcp14>",
			"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to
			be interpreted as
			described in BCP 14 <xref target="RFC2119" format="default" sectionFormat="o
			f" derivedContent="RFC2119"/> <xref target="RFC8174" format="default" sectionFor
			mat="of" derivedContent="RFC8174"/>
			when, and only when, they appear in all capitals, as shown here.
	</t>		</t>
	</section>		</section>
	<!--
	<section removeInRFC="true">
	<name>Open Issues</name>
	<ul>
	<li>
	No Open Issues
	</li>
	</ul>
	</section>
	-->
	</section>		</section>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-2">
	<section>		<name slugifiedName="name-hash-algorithm-usage">Hash Algorithm Usage</name
	<name>Hash Algorithm Usage</name>		>
			<t indent="0" pn="section-2-1">
	<t>		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 varie		variety of purposes.
	ty of purposes.
	Some of these purposes require that a hash function be cryptographically strong.		Some of these purposes require that a hash function be cryptographically strong.
	These include direct and indirect signatures.		These include direct and indirect signatures -- that is, using the
	That is, using the hash as part of the signature or using the hash as pa		hash as part of the signature or using the hash as part of the body to
	rt of the body to be signed.		be signed.
	Other uses of hash functions may not require the same level of strength.		Other uses of hash functions may not require the same level of strength.
	</t>		</t>
			<t indent="0" pn="section-2-2">
	<t>
	This document contains some hash functions that are not designed to be u sed for cryptographic operations.		This document contains some hash functions that are not designed to be u sed 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 p rovide them.		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 p rovide them.
	Applications should also make sure that the ability to change hash funct		Applications should also make sure that the ability to change hash
	ions is part of the base design, as cryptographic advances are sure to reduce th		functions is part of the base design, as cryptographic advances are sure to
	e strength of a hash function <xref target="BCP201"/>.		reduce the strength of any given hash function <xref target="BCP201" format="def
			ault" sectionFormat="of" derivedContent="BCP201"/>.
	</t>		</t>
			<t indent="0" pn="section-2-3">
	<t>
	A hash function is a map from one, normally large, bit string to a secon d, usually smaller, bit string.		A hash function is a map from one, normally large, bit string to a secon d, usually smaller, bit string.
	As the number of possible input values is far greater than the number of possible output values, it is inevitable that there are going to be collisions.		As the number of possible input values is far greater than the number of possible output values, it is inevitable that there are going to be collisions.
	The trick is to make sure that it is difficult to find two values that a re going to map to the same output value.		The trick is to make sure that it is difficult to find two values that a re going to map to the same output value.
	A "Collision Attack" is one where an attacker can find two different mes sages that have the same hash value.		A "Collision Attack" is one where an attacker can find two different mes sages that have the same hash value.
	A hash function that is susceptible to practical collision attacks, <bcp		A hash function that is susceptible to practical collision attacks <bcp1
	14>SHOULD NOT</bcp14> be used for a cryptographic purpose.		4>SHOULD NOT</bcp14> be used for a cryptographic purpose.
	The discovery of theoretical collision attacks against a given hash func		The discovery of theoretical collision attacks against a given hash
	tion <bcp14>SHOULD</bcp14> trigger protocol maintainers and users to do a review		function <bcp14>SHOULD</bcp14> trigger protocol maintainers and users
	of the continued suitability of the algorithm if alternatives are available and		to review the continued suitability of the algorithm if
	migration is viable.		alternatives are available and migration is viable.
	The only reason why such a hash function is used is when there is absolu		The only reason such a hash function is used is when there is
	tely no other choice (e.g. a Hardware Security Module (HSM) that cannot be repla		absolutely no other choice (e.g., a Hardware Security Module (HSM)
	ced), and only after looking at the possible security issues.		that cannot be replaced), and only after looking at the possible
			security issues.
	Cryptographic purposes would include the creation of signatures or the u se of hashes for indirect signatures.		Cryptographic purposes would include the creation of signatures or the u se of hashes for indirect signatures.
	These functions may still be usable for non-cryptographic purposes.		These functions may still be usable for noncryptographic purposes.
	</t>		</t>
			<t indent="0" pn="section-2-4">
	<t>		An example of a noncryptographic use of a hash is filtering from a
	An example of a non-cryptographic use of a hash is for filtering from a		collection of values to find a set of possible candidates; the
	collection of values to find a set of possible candidates; the candidates can th		candidates can then be checked to see if they can successfully be
	en be checked to see if they can successfully be used.		used.
	A simple example of this is the classic fingerprint of a certificate.		A simple example of this is the classic fingerprint of a certificate.
	If the fingerprint is used to verify that it is the correct certificate, then that usage is a cryptographic one and is subject to the warning above abou t collision attack.		If the fingerprint is used to verify that it is the correct certificate, then that usage is a cryptographic one and is subject to the warning above abou t collision attack.
	If, however, the fingerprint is used to sort through a collection of cer tificates to find those that might be used for the purpose of verifying a signat ure, a simple filter capability is sufficient.		If, however, the fingerprint is used to sort through a collection of cer tificates to find those that might be used for the purpose of verifying a signat ure, a simple filter capability is sufficient.
	In this case, one still needs to confirm that the public key validates t		In this case, one still needs to confirm that the public key validates
	he signature (and the certificate is trusted), and all certificates that don't c		the signature (and that the certificate is trusted), and all certificates that d
	ontain a key that validates the signature can be discarded as false positives.		on't contain a key that validates the signature can be discarded as false positi
			ves.
	</t>		</t>
			<t indent="0" pn="section-2-5">
	<t>		To distinguish between these two cases, a new value in the Recommended
	To distinguish between these two cases, a new value in the recommended c		column of the "COSE Algorithms" registry has been added.
	olumn 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		should be to filter results; it is not intended for applications that
	be to filter results and it is not intended for applications which require a cry		require a cryptographically strong algorithm.
	ptographically strong algorithm.
	</t>		</t>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-2.1
	<section>		">
	<name>		<name slugifiedName="name-example-cbor-hash-structure">
	Example CBOR hash structure		Example CBOR Hash Structure
	</name>		</name>
			<t indent="0" pn="section-2.1-1">
	<t>		<xref target="RFC8152" format="default" sectionFormat="of" derivedCont
	<xref target="RFC8152"/> did not provide a default structure for holdi		ent="COSE"/> did not provide a default structure for
	ng a hash value not only because no separate hash algorithms were defined, but b		holding a hash value both because no separate hash algorithms
	ecause how the structure is setup is frequently application specific.		were defined and because the way the structure is set up is frequently
			application specific.
	There are four fields that are often included as part of a hash struct ure:		There are four fields that are often included as part of a hash struct ure:
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-2
	<ul>		.1-2">
	<li>		<li pn="section-2.1-2.1">
	The hash algorithm identifier.		The hash algorithm identifier.
	</li>		</li>
	<li>		<li pn="section-2.1-2.2">
	The hash value.		The hash value.
	</li>		</li>
	<li>		<li pn="section-2.1-2.3">
	A pointer to the value that was hashed.		A pointer to the value that was hashed.
	This could be a pointer to a file, an object that can be obtained fr		This could be a pointer to a file, an object that can be obtained
	om the network, or a pointer to someplace in the message, or something very appl		from the network, a pointer to someplace in the message, or
	ication specific.		something very application specific.
	</li>		</li>
	<li>		<li pn="section-2.1-2.4">
	Additional data; this can be something as simple as a random value (		Additional data. This can be something as simple as a random value
	i.e. salt) to make finding hash collisions slightly harder (as the payload hande		(i.e., salt) to make finding hash collisions slightly harder (because
	d to the application could have been selected to have a collision), or as compli		the payload handed to the application could have been selected to
	cated as a set of processing instructions that are used with the object that is		have a collision), or as complicated as a set of processing
	pointed to.		instructions that is used with the object that is pointed to.
	The additional data can be dealt with in a number of ways, prependin		The additional data can be dealt with in a number of ways,
	g or appending to the content, but it is strongly suggested that it either be a		prepending or appending to the content, but it is strongly
	fixed known size, or the lengths of the pieces being hashed be included.		suggested that either it be a fixed known size, or the lengths of
			the pieces being hashed be included so that the resulting byte
			string has a unique interpretation as the additional data.
	(Encoding as a CBOR array accomplishes this requirement.)		(Encoding as a CBOR array accomplishes this requirement.)
	</li>		</li>
	</ul>		</ul>
			<t indent="0" pn="section-2.1-3">
	<t>		An example of a structure that permits all of the above fields to exis
	An example of a structure which permits all of the above fields to exi		t would look like the following:
	st would look like the following.
	</t>		</t>
			<sourcecode type="cddl" markers="false" pn="section-2.1-4">
	<sourcecode type="CDDL">
	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 that was 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
	)		)
	</sourcecode>		</sourcecode>
			<t indent="0" pn="section-2.1-5">
	<t>
	Below is an alternative structure that could be used in situations whe re one is searching a group of objects for a matching hash value.		Below is an alternative structure that could be used in situations whe re one is searching a group of objects for a matching hash value.
	In this case, the location would not be needed and adding extra data t o the hash would be counterproductive.		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:		This results in a structure that looks like this:
	</t>		</t>
			<sourcecode type="cddl" markers="false" pn="section-2.1-6">
	<sourcecode type="CDDL">
	COSE_Hash_Find = [		COSE_Hash_Find = [
	hashAlg : int / tstr,		hashAlg : int / tstr,
	hashValue : bstr		hashValue : bstr
	]		]
	</sourcecode>		</sourcecode>
	</section>		</section>
	</section>		</section>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-3">
	<section>		<name slugifiedName="name-hash-algorithm-identifiers">Hash Algorithm Ident
	<name>Hash Algorithm Identifiers</name>		ifiers</name>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-3.1
	<section>		">
	<name>SHA-1 Hash Algorithm</name>		<name slugifiedName="name-sha-1-hash-algorithm">SHA-1 Hash Algorithm</na
	<t>		me>
	The SHA-1 hash algorithm <xref target="RFC3174"/> was designed by th		<t indent="0" pn="section-3.1-1">
	e United States National Security Agency and published in 1995.		The SHA-1 hash algorithm <xref target="RFC3174" format="default" sec
	Since that time a large amount of cryptographic analysis has been ap		tionFormat="of" derivedContent="RFC3174"/> was designed by
	plied to this algorithm and a successful collision attack has been created (<xre		the United States National Security Agency and published in
	f target="SHA-1-collision"/>).		1995. Since that time, a large amount of cryptographic analysis
	The IETF formally started discouraging the use of SHA-1 with the pub		has been applied to this algorithm, and a successful collision
	lishing of <xref target="RFC6194"/>.		attack has been created <xref target="SHA-1-collision" format="defaul
	</t>		t" sectionFormat="of" derivedContent="SHA-1-collision"/>.
			The IETF formally started discouraging the use of SHA-1 in <xref tar
	<!-- RFC Editor -		get="RFC6194" format="default" sectionFormat="of" derivedContent="RFC6194"/>.
	I had an original comment that the grammar of the "or where" clau		</t>
	se did not match with the start of the sentence.		<t indent="0" pn="section-3.1-2">
	I re-wrote the second sentence but it is possible that I still ha		Despite these facts, there are still times where SHA-1 needs to be
	ve the same problem.		used; therefore, it makes sense to assign a code point for the
	-->		use of this hash algorithm.
	<t>		Some of these situations involve historic HSMs where only SHA-1 is
	Despite the above, there are still times where SHA-1 needs to be use		implemented; in other situations, the SHA-1 value is used
	d and therefore it makes sense to assign a codepoint for the use of this hash al		for the purpose of filtering; thus, the collision-resistance
	gorithm.		property is not needed.
	Some of these situations are with historic HSMs where only SHA-1 is		</t>
	implemented; other situations are where the SHA-1 value is used for the purpose		<t indent="0" pn="section-3.1-3">
	of filtering and thus the collision resistance property is not needed.
	</t>
	<t>
	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 recommendation of "Fi lter Only".		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 recommendation of "Fi lter Only".
	This provides guidance about when the algorithm is safe for use, whi le discouraging usage where it is not safe.		This provides guidance about when the algorithm is safe for use, whi le discouraging usage where it is not safe.
	</t>		</t>
			<t indent="0" pn="section-3.1-4">
	<t>
	The COSE capabilities for this algorithm is an empty array.		The COSE capabilities for this algorithm is an empty array.
	</t>		</t>
			<table align="center" anchor="SHA1-Algs" pn="table-1">
	<table align="center" anchor="SHA1-Algs">		<name slugifiedName="name-sha-1-hash-algorithm-2">SHA-1 Hash Algorithm
	<name>SHA-1 Hash Algorithm</name>		</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="left" colspan="1" rowspan="1">Value</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	<th>Capabilities</th>		<th align="left" colspan="1" rowspan="1">Capabilities</th>
	<th>Reference</th>		<th align="left" colspan="1" rowspan="1">Reference</th>
	<th>Recommended</th>		<th align="left" colspan="1" rowspan="1">Recommended</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>SHA-1</td>		<td align="left" colspan="1" rowspan="1">SHA-1</td>
	<td>-14</td>		<td align="left" colspan="1" rowspan="1">-14</td>
	<td>SHA-1 Hash</td>		<td align="left" colspan="1" rowspan="1">SHA-1 Hash</td>
	<td>[]</td>		<td align="left" colspan="1" rowspan="1">[]</td>
	<td>[This Document]</td>		<td align="left" colspan="1" rowspan="1">RFC 9054</td>
	<td>Filter Only</td>		<td align="left" colspan="1" rowspan="1">Filter Only</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
			</section>
	</section>		<section numbered="true" removeInRFC="false" toc="include" pn="section-3.2
			">
	<section>		<name slugifiedName="name-sha-2-hash-algorithms">SHA-2 Hash Algorithms</
	<name>SHA-2 Hash Algorithms</name>		name>
	<t>		<t indent="0" pn="section-3.2-1">
	The family of SHA-2 hash algorithms <xref target="FIPS-180-4"/> was de		The family of SHA-2 hash algorithms <xref target="FIPS-180-4" format="
	signed by the United States National Security Agency and published in 2001.		default" sectionFormat="of" derivedContent="FIPS-180-4"/> was designed by the Un
	Since that time some additional algorithms have been added to the orig		ited States National Security Agency and published in 2001.
	inal set to deal with length extension attacks and some performance issues.		Since that time, some additional algorithms have been added to the ori
			ginal set to deal with length-extension attacks and some performance issues.
	While the SHA-3 hash algorithms have been published since that time, t he SHA-2 algorithms are still broadly used.		While the SHA-3 hash algorithms have been published since that time, t he SHA-2 algorithms are still broadly used.
	</t>		</t>
			<t indent="0" pn="section-3.2-2">
	<t>
	There are a number of different parameters for the SHA-2 hash function s.		There are a number of different parameters for the SHA-2 hash function s.
	The set of hash functions which have been chosen for inclusion in this		The set of hash functions that has been chosen for inclusion in
	document are based on those different parameters and some of the trade-offs inv		this document is based on those different parameters and some of
	olved.		the trade-offs involved.
	</t>		</t>
	<ul>		<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-3
	<li>		.2-3">
	<t>		<li pn="section-3.2-3.1">
			<t indent="0" pn="section-3.2-3.1.1">
	<strong>SHA-256/64</strong> provides a truncated hash.		<strong>SHA-256/64</strong> provides a truncated hash.
	The length of the truncation is designed to allow for smaller tran smission size.		The length of the truncation is designed to allow for smaller tran smission size.
	The trade-off is that the odds that a collision will occur increas e proportionally.		The trade-off is that the odds that a collision will occur increas e proportionally.
	Use of this hash function needs analysis of the potential problems		Use of this hash function requires analysis of the potential
	with having a collision occur, or must be limited to where the function of the		problems that could result from a collision, or it must be
	hash is non-cryptographic.		limited to where the purpose of the hash is noncryptographic.
	</t>		</t>
	<t>		<t indent="0" pn="section-3.2-3.1.2">
	The latter is the case for <xref target="I-D.ietf-cose-x509"/>.		The latter is the case for some of the scenarios identified in <
	The hash value is used to select possible certificates and, if t		xref target="I-D.ietf-cose-x509" format="default" sectionFormat="of" derivedCont
	here are multiple choices remaining then, each choice can be tested by using the		ent="COSE-x509"/>,
	public key.		specifically, for the cases when the hash value is used to selec
	</t>		t among possible certificates: if
	</li>		there are multiple choices remaining, then each choice can be
	<li>		tested by using the public key.
	<strong>SHA-256</strong> is probably the most common hash function		</t>
	used currently.		</li>
			<li pn="section-3.2-3.2">
			<strong>SHA-256</strong> is probably the most common hash function u
			sed currently.
	SHA-256 is an efficient hash algorithm for 32-bit hardware.		SHA-256 is an efficient hash algorithm for 32-bit hardware.
	</li>		</li>
	<li>		<li pn="section-3.2-3.3">
	<strong>SHA-384</strong> and <strong>SHA-512</strong> hash functio		<strong>SHA-384</strong> and <strong>SHA-512</strong> hash functions
	ns are efficient for 64-bit hardware.		are efficient for 64-bit hardware.
	</li>		</li>
	<li>		<li pn="section-3.2-3.4">
	<strong>SHA-512/256</strong> provides a hash function that runs mo		<strong>SHA-512/256</strong> provides a hash function that runs more
	re efficiently on 64-bit hardware, but offers the same security levels as SHA-25		efficiently on 64-bit hardware but offers the same security level as SHA-256.
	6.
	</li>		</li>
	</ul>		</ul>
			<aside pn="section-3.2-4">
	<t>		<t indent="0" pn="section-3.2-4.1">NOTE: SHA-256/64 is a simple trunca
			tion of SHA-256 to 64 bits defined in this specification. SHA-512/256 is a modif
			ied variant of SHA-512 truncated to 256 bits, as defined in <xref target="FIPS-1
			80-4" format="default" sectionFormat="of" derivedContent="FIPS-180-4"/>.</t>
			</aside>
			<t indent="0" pn="section-3.2-5">
	The COSE capabilities array for these algorithms is empty.		The COSE capabilities array for these algorithms is empty.
	</t>		</t>
			<table align="center" anchor="SHA2-Algs" pn="table-2">
	<table align="center" anchor="SHA2-Algs">		<name slugifiedName="name-sha-2-hash-algorithms-2">SHA-2 Hash Algorith
	<name>SHA-2 Hash Algorithms</name>		ms</name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="left" colspan="1" rowspan="1">Value</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	<th>Capabilities</th>		<th align="left" colspan="1" rowspan="1">Capabilities</th>
	<th>Reference</th>		<th align="left" colspan="1" rowspan="1">Reference</th>
	<th>Recommended</th>		<th align="left" colspan="1" rowspan="1">Recommended</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>SHA-256/64</td>		<td align="left" colspan="1" rowspan="1">SHA-256/64</td>
	<td>-15</td>		<td align="left" colspan="1" rowspan="1">-15</td>
	<td>SHA-2 256-bit Hash truncated to 64-bits</td>		<td align="left" colspan="1" rowspan="1">SHA-2 256-bit Hash trunca
	<td>[]</td>		ted to 64-bits</td>
	<td>[This Document]</td>		<td align="left" colspan="1" rowspan="1">[]</td>
	<td>Filter Only</td>		<td align="left" colspan="1" rowspan="1">RFC 9054</td>
			<td align="left" colspan="1" rowspan="1">Filter Only</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>SHA-256</td>		<td align="left" colspan="1" rowspan="1">SHA-256</td>
	<td>-16</td>		<td align="left" colspan="1" rowspan="1">-16</td>
	<td>SHA-2 256-bit Hash</td>		<td align="left" colspan="1" rowspan="1">SHA-2 256-bit Hash</td>
	<td>[]</td>		<td align="left" colspan="1" rowspan="1">[]</td>
	<td>[This Document]</td>		<td align="left" colspan="1" rowspan="1">RFC 9054</td>
	<td>Yes</td>		<td align="left" colspan="1" rowspan="1">Yes</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>SHA-384</td>		<td align="left" colspan="1" rowspan="1">SHA-384</td>
	<td>-43</td>		<td align="left" colspan="1" rowspan="1">-43</td>
	<td>SHA-2 384-bit Hash</td>		<td align="left" colspan="1" rowspan="1">SHA-2 384-bit Hash</td>
	<td>[]</td>		<td align="left" colspan="1" rowspan="1">[]</td>
	<td>[This Document]</td>		<td align="left" colspan="1" rowspan="1">RFC 9054</td>
	<td>Yes</td>		<td align="left" colspan="1" rowspan="1">Yes</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>SHA-512</td>		<td align="left" colspan="1" rowspan="1">SHA-512</td>
	<td>-44</td>		<td align="left" colspan="1" rowspan="1">-44</td>
	<td>SHA-2 512-bit Hash</td>		<td align="left" colspan="1" rowspan="1">SHA-2 512-bit Hash</td>
	<td>[]</td>		<td align="left" colspan="1" rowspan="1">[]</td>
	<td>[This Document]</td>		<td align="left" colspan="1" rowspan="1">RFC 9054</td>
	<td>Yes</td>		<td align="left" colspan="1" rowspan="1">Yes</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>SHA-512/256</td>		<td align="left" colspan="1" rowspan="1">SHA-512/256</td>
	<td>-17</td>		<td align="left" colspan="1" rowspan="1">-17</td>
	<td>SHA-2 512-bit Hash truncated to 256-bits</td>		<td align="left" colspan="1" rowspan="1">SHA-2 512-bit Hash trunca
	<td>[]</td>		ted to 256-bits</td>
	<td>[This Document]</td>		<td align="left" colspan="1" rowspan="1">[]</td>
	<td>Yes</td>		<td align="left" colspan="1" rowspan="1">RFC 9054</td>
			<td align="left" colspan="1" rowspan="1">Yes</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	</section>		</section>
			<section numbered="true" removeInRFC="false" toc="include" pn="section-3.3
	<section>		">
	<name>SHAKE Algorithms</name>		<name slugifiedName="name-shake-algorithms">SHAKE Algorithms</name>
			<t indent="0" pn="section-3.3-1">
	<t>		The family of SHA-3 hash algorithms <xref target="FIPS-202" format="de
	The family of SHA-3 hash algorithms <xref target="FIPS-202"/> was the		fault" sectionFormat="of" derivedContent="FIPS-202"/> was the result of a compet
	result of a competition run by NIST.		ition run by NIST.
	The pair of algorithms known as SHAKE-128 and SHAKE-256 are the instan ces of SHA-3 that are currently being standardized in the IETF.		The pair of algorithms known as SHAKE-128 and SHAKE-256 are the instan ces of SHA-3 that are currently being standardized in the IETF.
	<!-- Check with Roman - maybe delete -->
	This is the reason for including these algorithms in this document.		This is the reason for including these algorithms in this document.
	</t>		</t>
			<t indent="0" pn="section-3.3-2">
	<t>
	The SHA-3 hash algorithms have a significantly different structure tha n the SHA-2 hash algorithms.		The SHA-3 hash algorithms have a significantly different structure tha n the SHA-2 hash algorithms.
	</t>		</t>
			<t indent="0" pn="section-3.3-3">
	<t>
	Unlike the SHA-2 hash functions, no algorithm identifier is created fo r shorter lengths.		Unlike the SHA-2 hash functions, no algorithm identifier is created fo r shorter lengths.
	The length of the hash value stored is 256-bits for SHAKE-128 and 512-		The length of the hash value stored is 256 bits for SHAKE-128 and
	bits for SHAKE-256.		512 bits for SHAKE-256.
	</t>		</t>
			<t indent="0" pn="section-3.3-4">
	<t>
	The COSE capabilities array for these algorithms is empty.		The COSE capabilities array for these algorithms is empty.
	</t>		</t>
			<table align="center" anchor="SHAKE-Algs" pn="table-3">
	<table align="center" anchor="SHAKE-Algs">		<name slugifiedName="name-shake-hash-functions">SHAKE Hash Functions</
	<name>SHAKE Hash Functions</name>		name>
	<thead>		<thead>
	<tr>		<tr>
	<th>Name</th>		<th align="left" colspan="1" rowspan="1">Name</th>
	<th>Value</th>		<th align="left" colspan="1" rowspan="1">Value</th>
	<th>Description</th>		<th align="left" colspan="1" rowspan="1">Description</th>
	<th>Capabilities</th>		<th align="left" colspan="1" rowspan="1">Capabilities</th>
	<th>Reference</th>		<th align="left" colspan="1" rowspan="1">Reference</th>
	<th>Recommended</th>		<th align="left" colspan="1" rowspan="1">Recommended</th>
	</tr>		</tr>
	</thead>		</thead>
	<tbody>		<tbody>
	<tr>		<tr>
	<td>SHAKE128</td>		<td align="left" colspan="1" rowspan="1">SHAKE128</td>
	<td>-18</td>		<td align="left" colspan="1" rowspan="1">-18</td>
	<td>SHAKE-128 256-bit Hash Value</td>		<td align="left" colspan="1" rowspan="1">SHAKE-128 256-bit Hash Va
	<td>[]</td>		lue</td>
	<td>[This Document]</td>		<td align="left" colspan="1" rowspan="1">[]</td>
	<td>Yes</td>		<td align="left" colspan="1" rowspan="1">RFC 9054</td>
			<td align="left" colspan="1" rowspan="1">Yes</td>
	</tr>		</tr>
	<tr>		<tr>
	<td>SHAKE256</td>		<td align="left" colspan="1" rowspan="1">SHAKE256</td>
	<td>-45</td>		<td align="left" colspan="1" rowspan="1">-45</td>
	<td>SHAKE-256 512-bit Hash Value</td>		<td align="left" colspan="1" rowspan="1">SHAKE-256 512-bit Hash Va
	<td>[]</td>		lue</td>
	<td>[This Document]</td>		<td align="left" colspan="1" rowspan="1">[]</td>
	<td>Yes</td>		<td align="left" colspan="1" rowspan="1">RFC 9054</td>
			<td align="left" colspan="1" rowspan="1">Yes</td>
	</tr>		</tr>
	</tbody>		</tbody>
	</table>		</table>
	</section>		</section>
	</section>		</section>
			<section anchor="iana-considerations" numbered="true" removeInRFC="false" to
	<section anchor="iana-considerations">		c="include" pn="section-4">
	<name>IANA Considerations</name>		<name slugifiedName="name-iana-considerations">IANA Considerations</name>
	<!-- RFC Editor		<section anchor="cose-algorithm-registry" numbered="true" removeInRFC="fal
	I think that this paragraph can be removed before publishing.		se" toc="include" pn="section-4.1">
	-->		<name slugifiedName="name-cose-algorithm-registry">COSE Algorithm Regist
	<t>		ry</name>
	The IANA actions in <xref target="I-D.ietf-cose-rfc8152bis-struct"/> and		<t indent="0" pn="section-4.1-1">
	<xref target="I-D.ietf-cose-rfc8152bis-algs"/> need to be executed before the a		IANA has registered the following algorithms in the <eref target="http
	ctions in this document.		s://www.iana.org/assignments/cose/" brackets="none">"COSE Algorithms" registry</
	Where early allocation of codepoints has been made, these should be pres		eref>.
	erved.
	</t>
	<section anchor="cose-algorithm-registry">
	<name>COSE Algorithm Registry</name>
	<t>
	IANA is requested to register the following algorithms in the "COSE Al
	gorithms" registry.
	</t>		</t>
			<ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4
	<ul>		.1-2">
	<li>		<li pn="section-4.1-2.1">
	The SHA-1 hash function found in <xref target="SHA1-Algs"/>.		The SHA-1 hash function found in <xref target="SHA1-Algs" format="de
			fault" sectionFormat="of" derivedContent="Table 1"/>.
	</li>		</li>
	<li>		<li pn="section-4.1-2.2">
	The set of SHA-2 hash functions found in <xref target="SHA2-Algs"/>.		The set of SHA-2 hash functions found in <xref target="SHA2-Algs" fo
			rmat="default" sectionFormat="of" derivedContent="Table 2"/>.
	</li>		</li>
	<li>		<li pn="section-4.1-2.3">
	The set of SHAKE hash functions found in <xref target="SHAKE-Algs"/>		The set of SHAKE hash functions found in <xref target="SHAKE-Algs" f
	.		ormat="default" sectionFormat="of" derivedContent="Table 3"/>.
	</li>		</li>
	</ul>		</ul>
			<t indent="0" pn="section-4.1-3">
	<!-- IANA		Many of the hash values produced are relatively long; as such,
	The following paragraph is retained for historic reasons only.		use of a two-byte algorithm identifier seems reasonable.
	-->		SHA-1 is tagged as "Filter Only", so a longer algorithm identifier is
			appropriate even though it is a shorter hash value.
	<t>
	Many of the hash values produced are relatively long and as such the u
	se of a two byte algorithm identifier seems reasonable.
	SHA-1 is tagged as 'Filter Only' and thus a longer algorithm identifie
	r is appropriate even though it is a shorter hash value.
	</t>		</t>
			<t indent="0" pn="section-4.1-4">
			IANA has added 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 that require collision
			resistance. As a result of this addition, IANA has added this document
			as a reference for the "COSE Algorithms" registry.
	<t>
	IANA is requested to add the value of 'Filter Only' to the set of lega
	l 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.
	IANA is requested to add this document to the reference section for th
	is table due to this addition.
	</t>		</t>
	</section>		</section>
	</section>		</section>
			<section anchor="security-considerations" numbered="true" removeInRFC="false
	<section anchor="security-considerations">		" toc="include" pn="section-5">
	<name>Security Considerations</name>		<name slugifiedName="name-security-considerations">Security Considerations
	<t>		</name>
			<t indent="0" pn="section-5-1">
	Protocols need to perform a careful analysis of the properties of a ha sh function that are needed and how they map onto the possible attacks.		Protocols need to perform a careful analysis of the properties of a ha sh function that are needed and how they map onto the possible attacks.
	In particular, one needs to distinguish between those uses that need t he cryptographic properties, such as collision resistance, and properties that c orrespond to possible object identification.		In particular, one needs to distinguish between those uses that need t he cryptographic properties, such as collision resistance, and uses that only ne ed 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?		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-ima ge resistance.		This is the difference between collision resistance and second pre-ima ge resistance.
	As a general rule, longer hash values are "better" than short ones, bu t trade-offs of transmission size, timeliness, and security all need to be inclu ded as part of this analysis.		As a general rule, longer hash values are "better" than short ones, bu t trade-offs of transmission size, timeliness, and security all need to be inclu ded as part of this analysis.
	In many cases the value being hashed is a public value and, as such, p		In many cases, the value being hashed is a public value and, as
	re-image resistance is not part of this analysis.		such, (first) pre-image resistance is not part of this analysis.
	</t>		</t>
	<t>		<t indent="0" pn="section-5-2">
	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 <xref target="BCP201"/>.		hash functions <xref target="BCP201" format="default" sectionFormat="of" derived
	As with any cryptographic function, hash functions are under constant		Content="BCP201"/>.
	attack and the cryptographic strength of hash algorithms will be reduced over ti		As with any cryptographic function, hash functions are under
	me.		constant attack, and the cryptographic strength of hash algorithms
	</t>		will be reduced over time.
			</t>
	</section>		</section>
	</middle>		</middle>
			<back>
	<back xmlns:xi="http://www.w3.org/2001/XInclude" xml:base="http://xml2rfc.ietf
	.org/public/rfc/">
	<displayreference target="RFC2634" to="ESS"/>		<displayreference target="RFC2634" to="ESS"/>
	<displayreference target="RFC5652" to="CMS"/>		<displayreference target="RFC5652" to="CMS"/>
	<displayreference target="RFC8152" to="COSE"/>		<displayreference target="RFC8152" to="COSE"/>
			<displayreference target="I-D.ietf-cose-x509" to="COSE-x509"/>
			<displayreference target="I-D.ietf-suit-manifest" to="SUIT-MANIFEST"/>
			<references pn="section-6">
			<name slugifiedName="name-references">References</name>
			<references pn="section-6.1">
			<name slugifiedName="name-normative-references">Normative References</na
			me>
			<reference anchor="FIPS-180-4" quoteTitle="true" target="https://doi.org
			/10.6028/NIST.FIPS.180-4" derivedAnchor="FIPS-180-4">
			<front>
			<title>Secure Hash Standard</title>
			<author>
			<organization showOnFrontPage="true">NIST</organization>
			</author>
			<date month="August" year="2015"/>
			</front>
			<seriesInfo name="FIPS PUB" value="180-4"/>
			<seriesInfo name="DOI" value="10.6028/NIST.FIPS.180-4"/>
			</reference>
			<reference anchor="FIPS-202" quoteTitle="true" target="https://doi.org/1
			0.6028/NIST.FIPS.202" derivedAnchor="FIPS-202">
			<front>
			<title>SHA-3 Standard: Permutation-Based Hash and Extendable-Output
			Functions</title>
			<author initials="M.J." surname="Dworkin">
			<organization showOnFrontPage="true">National Institute of Standar
			ds and Technology</organization>
			</author>
			<date month="August" year="2015"/>
			</front>
			<seriesInfo name="FIPS PUB" value="202"/>
			<seriesInfo name="DOI" value="10.6028/NIST.FIPS.202"/>
			</reference>
			<reference anchor="RFC2119" target="https://www.rfc-editor.org/info/rfc2
			119" quoteTitle="true" derivedAnchor="RFC2119">
			<front>
			<title>Key words for use in RFCs to Indicate Requirement Levels</tit
			le>
			<author initials="S." surname="Bradner" fullname="S. Bradner">
			<organization showOnFrontPage="true"/>
			</author>
			<date year="1997" month="March"/>
			<abstract>
			<t indent="0">In many standards track documents several words are
			used to signify the requirements in the specification. These words are often ca
			pitalized. This document defines these words as they should be interpreted in IE
			TF documents. This document specifies an Internet Best Current Practices for th
			e Internet Community, and requests discussion and suggestions for improvements.<
			/t>
			</abstract>
			</front>
			<seriesInfo name="BCP" value="14"/>
			<seriesInfo name="RFC" value="2119"/>
			<seriesInfo name="DOI" value="10.17487/RFC2119"/>
			</reference>
			<reference anchor="RFC3174" target="https://www.rfc-editor.org/info/rfc3
			174" quoteTitle="true" derivedAnchor="RFC3174">
			<front>
			<title>US Secure Hash Algorithm 1 (SHA1)</title>
			<author initials="D." surname="Eastlake 3rd" fullname="D. Eastlake 3
			rd">
			<organization showOnFrontPage="true"/>
			</author>
			<author initials="P." surname="Jones" fullname="P. Jones">
			<organization showOnFrontPage="true"/>
			</author>
			<date year="2001" month="September"/>
			<abstract>
			<t indent="0">The purpose of this document is to make the SHA-1 (S
			ecure Hash Algorithm 1) hash algorithm conveniently available to the Internet co
			mmunity. This memo provides information for the Internet community.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="3174"/>
			<seriesInfo name="DOI" value="10.17487/RFC3174"/>
			</reference>
			<reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8
			174" quoteTitle="true" derivedAnchor="RFC8174">
			<front>
			<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
			tle>
			<author fullname="B. Leiba" surname="Leiba"/>
			<date month="May" year="2017"/>
			<abstract>
			<t indent="0">RFC 2119 specifies common key words that may be used
			in protocol specifications. This document aims to reduce the ambiguity by clar
			ifying that only UPPERCASE usage of the key words have the defined special meani
			ngs.</t>
			</abstract>
			</front>
			<seriesInfo name="BCP" value="14"/>
			<seriesInfo name="RFC" value="8174"/>
			<seriesInfo name="DOI" value="10.17487/RFC8174"/>
			</reference>
			<reference anchor="RFC9052" target="https://www.rfc-editor.org/info/rfc9
			052" quoteTitle="true" derivedAnchor="RFC9052">
			<front>
			<title>CBOR Object Signing and Encryption (COSE): Structures and Pro
			cess</title>
			<author initials="J" surname="Schaad" fullname="Jim Schaad">
			<organization showOnFrontPage="true"/>
			</author>
			<date month="August" year="2022"/>
			</front>
			<seriesInfo name="STD" value="96"/>
			<seriesInfo name="RFC" value="9052"/>
			<seriesInfo name="DOI" value="10.17487/RFC9052"/>
			</reference>
			</references>
			<references pn="section-6.2">
			<name slugifiedName="name-informative-references">Informative References
			</name>
			<reference anchor="BCP201" target="https://www.rfc-editor.org/info/bcp20
			1" quoteTitle="true" derivedAnchor="BCP201">
			<front>
			<title>Guidelines for Cryptographic Algorithm Agility and Selecting
			Mandatory-to-Implement Algorithms</title>
			<author initials="R." surname="Housley" fullname="Russ Housley">
			<organization showOnFrontPage="true"/>
			</author>
			<date month="November" year="2015"/>
			</front>
			<seriesInfo name="BCP" value="201"/>
			<seriesInfo name="RFC" value="7696"/>
			</reference>
			<reference anchor="RFC5652" target="https://www.rfc-editor.org/info/rfc5
			652" quoteTitle="true" derivedAnchor="CMS">
			<front>
			<title>Cryptographic Message Syntax (CMS)</title>
			<author initials="R." surname="Housley" fullname="R. Housley">
			<organization showOnFrontPage="true"/>
			</author>
			<date year="2009" month="September"/>
			<abstract>
			<t indent="0">This document describes the Cryptographic Message Sy
			ntax (CMS). This syntax is used to digitally sign, digest, authenticate, or enc
			rypt arbitrary message content. [STANDARDS-TRACK]</t>
			</abstract>
			</front>
			<seriesInfo name="STD" value="70"/>
			<seriesInfo name="RFC" value="5652"/>
			<seriesInfo name="DOI" value="10.17487/RFC5652"/>
			</reference>
			<reference anchor="RFC8152" target="https://www.rfc-editor.org/info/rfc8
			152" quoteTitle="true" derivedAnchor="COSE">
			<front>
			<title>CBOR Object Signing and Encryption (COSE)</title>
			<author initials="J." surname="Schaad" fullname="J. Schaad">
			<organization showOnFrontPage="true"/>
			</author>
			<date year="2017" month="July"/>
			<abstract>
			<t indent="0">Concise Binary Object Representation (CBOR) is a dat
			a format designed for small code size and small message size. There is a need f
			or the ability to have basic security services defined for this data format. Thi
			s document defines the CBOR Object Signing and Encryption (COSE) protocol. This
			specification describes how to create and process signatures, message authentic
			ation codes, and encryption using CBOR for serialization. This specification ad
			ditionally describes how to represent cryptographic keys using CBOR.</t>
			</abstract>
			</front>
			<seriesInfo name="RFC" value="8152"/>
			<seriesInfo name="DOI" value="10.17487/RFC8152"/>
			</reference>
			<reference anchor="I-D.ietf-cose-x509" quoteTitle="true" target="https:/
			/datatracker.ietf.org/doc/html/draft-ietf-cose-x509-08" derivedAnchor="COSE-x509
			">
			<front>
			<title>CBOR Object Signing and Encryption (COSE): Header parameters
			for carrying and referencing X.509 certificates</title>
			<author fullname="Jim Schaad">
			<organization showOnFrontPage="true">August Cellars</organization>
			</author>
			<date month="December" day="14" year="2020"/>
			<abstract>
			<t indent="0"> The CBOR Signing And Encrypted Message (COSE) str
			ucture uses
			references to keys in general. For some algorithms, additional
			properties are defined which carry parameters relating to keys as
			needed. The COSE Key structure is used for transporting keys outside
			of COSE messages. This document extends the way that keys can be
			identified and transported by providing attributes that refer to or
			contain X.509 certificates.
	<references title='Normative References'>		</t>
	<xi:include href="bibxml/reference.RFC.2119.xml" />		</abstract>
	<xi:include href="bibxml/reference.RFC.8174.xml" />		</front>
	<xi:include href="bibxml3/reference.I-D.ietf-cose-rfc8152bis-struct.xml" /		<seriesInfo name="Internet-Draft" value="draft-ietf-cose-x509-08"/>
	>		<format type="TXT" target="https://www.ietf.org/archive/id/draft-ietf-
			cose-x509-08.txt"/>
	<reference anchor="FIPS-180-4">		<refcontent>Work in Progress</refcontent>
	<front>		</reference>
	<title>Secure Hash Standard</title>		<reference anchor="RFC2634" target="https://www.rfc-editor.org/info/rfc2
	<author>		634" quoteTitle="true" derivedAnchor="ESS">
	<organization>National Institute of Standards and Technology</organi		<front>
	zation>		<title>Enhanced Security Services for S/MIME</title>
	</author>		<author initials="P." surname="Hoffman" fullname="P. Hoffman" role="
	<date month="August" year="2015"/>		editor">
	</front>		<organization showOnFrontPage="true"/>
	<seriesInfo name="FIPS" value="PUB 180-4"/>		</author>
	</reference>		<date year="1999" month="June"/>
			<abstract>
	<reference anchor="FIPS-202">		<t indent="0">This document describes four optional security servi
	<front>		ce extensions for S/MIME. [STANDARDS-TRACK]</t>
	<title>SHA-3 Standard: Permutation-Based Hash and Extendable-Output Fu		</abstract>
	nctions</title>		</front>
	<author>		<seriesInfo name="RFC" value="2634"/>
	<organization>National Institute of Standards and Technology</organi		<seriesInfo name="DOI" value="10.17487/RFC2634"/>
	zation>		</reference>
	</author>		<reference anchor="RFC6194" target="https://www.rfc-editor.org/info/rfc6
	<date month="August" year="2015"/>		194" quoteTitle="true" derivedAnchor="RFC6194">
	</front>		<front>
	<seriesInfo name="FIPS" value="PUB 202"/>		<title>Security Considerations for the SHA-0 and SHA-1 Message-Diges
	</reference>		t Algorithms</title>
			<author fullname="T. Polk" surname="Polk"/>
	<!--		<author fullname="L. Chen" surname="Chen"/>
	<?rfc include="bibxml/reference.RFC.5280.xml" />		<author fullname="S. Turner" surname="Turner"/>
	-->		<author fullname="P. Hoffman" surname="Hoffman"/>
			<date month="March" year="2011"/>
	<xi:include href="bibxml/reference.RFC.3174.xml" />		<abstract>
	</references>		<t indent="0">This document includes security considerations for t
			he SHA-0 and SHA-1 message digest algorithm. This document is not an Internet S
	<references title='Informative References'>		tandards Track specification; it is published for informational purposes.</t>
	<xi:include href="bibxml/reference.RFC.5652.xml"/>		</abstract>
	<xi:include href="bibxml/reference.RFC.2634.xml"/>		</front>
	<xi:include href="bibxml3/reference.I-D.ietf-cose-x509.xml"/>		<seriesInfo name="RFC" value="6194"/>
	<xi:include href="bibxml/reference.RFC.6194.xml"/>		<seriesInfo name="DOI" value="10.17487/RFC6194"/>
	<xi:include href="bibxml3/reference.I-D.ietf-cose-rfc8152bis-algs.xml"/>		</reference>
	<xi:include href="bibxml3/reference.I-D.ietf-suit-manifest.xml"/>		<reference anchor="SHA-1-collision" target="https://shattered.io/static/
			shattered.pdf" quoteTitle="true" derivedAnchor="SHA-1-collision">
	<!--		<front>
	<xi:include href="bibxml/reference.RFC.2585.xml"/>		<title>The first collision for full SHA-1</title>
	<xi:include href="bibxml/reference.RFC.5246.xml"/>		<author initials="M." surname="Stevens"/>
	<xi:include href="bibxml/reference.RFC.7468.xml"/>		<author initials="E." surname="Bursztein"/>
	<xi:include href="bibxml/reference.RFC.8152.xml"/>		<author initials="P." surname="Karpman"/>
	<xi:include href="bibxml/reference.RFC.8392.xml"/>		<author initials="A." surname="Albertini"/>
	<xi:include href="bibxml/reference.I-D.ietf-lamps-rfc5751-bis.xml"/>		<author initials="Y." surname="Markov"/>
	<xi:include href="bibxml/reference.I-D.ietf-cbor-cddl.xml"/>		<date month="Feb" year="2017"/>
	<xi:include href="bibxml/reference.I-D.selander-ace-cose-ecdhe.xml"/>		</front>
	-->		</reference>
			<reference anchor="I-D.ietf-suit-manifest" quoteTitle="true" target="htt
	<!-- <xi:include href="bibxml/reference.BCP.0201.xml"/> -->		ps://datatracker.ietf.org/doc/html/draft-ietf-suit-manifest-19" derivedAnchor="S
	<referencegroup anchor="BCP201" target="https://www.rfc-editor.org/info/bcp201">		UIT-MANIFEST">
	<!-- reference.RFC.7696.xml -->		<front>
	<reference anchor="RFC7696" target="https://www.rfc-editor.org/info/rfc7696">		<title>A Concise Binary Object Representation (CBOR)-based Serializa
	<front>		tion Format for the Software Updates for Internet of Things (SUIT) Manifest</tit
	<title>		le>
	Guidelines for Cryptographic Algorithm Agility and Selecting Mandatory-to-Implem		<author fullname="Brendan Moran">
	ent Algorithms		<organization showOnFrontPage="true">Arm Limited</organization>
	</title>		</author>
	<author initials="R." surname="Housley" fullname="R. Housley">		<author fullname="Hannes Tschofenig">
	<organization/>		<organization showOnFrontPage="true">Arm Limited</organization>
	</author>		</author>
	<date year="2015" month="November"/>		<author fullname="Henk Birkholz">
	<abstract>		<organization showOnFrontPage="true">Fraunhofer SIT</organization>
	<t>		</author>
	Many IETF protocols use cryptographic algorithms to provide confidentiality, int		<author fullname="Koen Zandberg">
	egrity, authentication, or digital signature. Communicating peers must support a		<organization showOnFrontPage="true">Inria</organization>
	common set of cryptographic algorithms for these mechanisms to work properly. T		</author>
	his memo provides guidelines to ensure that protocols have the ability to migrat		<date month="August" day="9" year="2022"/>
	e from one mandatory-to-implement algorithm suite to another over time.		<abstract>
	</t>		<t indent="0"> This specification describes the format of a mani
	</abstract>		fest. A manifest is
	</front>		a bundle of metadata about code/data obtained by a recipient (chiefly
	<seriesInfo name="BCP" value="201"/>		the firmware for an IoT device), where to find the that code/data,
	<seriesInfo name="RFC" value="7696"/>		the devices to which it applies, and cryptographic information
	<seriesInfo name="DOI" value="10.17487/RFC7696"/>		protecting the manifest. Software updates and Trusted Invocation
	</reference>		both tend to use sequences of common operations, so the manifest
	</referencegroup>		encodes those sequences of operations, rather than declaring the
			metadata.
	<reference anchor="SHA-1-collision" target="https://shattered.io/static/shattere		</t>
	d.pdf">		</abstract>
	<front>		</front>
	<title>The first collision for full SHA-1</title>		<seriesInfo name="Internet-Draft" value="draft-ietf-suit-manifest-19"/
	<author initials="M." surname="Stevens"/>		>
	<author initials="E." surname="Bursztein"/>		<format type="TXT" target="https://www.ietf.org/archive/id/draft-ietf-
	<author initials="P." surname="Karpman"/>		suit-manifest-19.txt"/>
	<author initials="A." surname="Albertini"/>		<refcontent>Work in Progress</refcontent>
	<author initials="Y." surname="Markov"/>		</reference>
	<date month="Feb" year="2017"/>		</references>
	</front>
	</reference>
	<xi:include href="bibxml/reference.RFC.8152.xml"/>
	</references>		</references>
			<section anchor="authors-addresses" numbered="false" removeInRFC="false" toc
			="include" pn="section-appendix.a">
			<name slugifiedName="name-authors-address">Author's Address</name>
			<author initials="J." surname="Schaad" fullname="Jim Schaad">
			<organization showOnFrontPage="true">August Cellars</organization>
			<address/>
			</author>
			</section>
	</back>		</back>
	</rfc>		</rfc>
End of changes. 81 change blocks.
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