rfc9679v2.txt		rfc9679.txt
	skipping to change at line 92 ¶		skipping to change at line 92 ¶
	function to a CBOR Object Signing and Encryption (COSE) Key structure		function to a CBOR Object Signing and Encryption (COSE) Key structure
	[RFC9052], resulting in a hash value known as a "thumbprint". To		[RFC9052], resulting in a hash value known as a "thumbprint". To
	achieve this, the document specifies which fields in the COSE Key		achieve this, the document specifies which fields in the COSE Key
	structure are included in the hash computation, the process for		structure are included in the hash computation, the process for
	creating a canonical form of these fields, and how to hash the		creating a canonical form of these fields, and how to hash the
	resulting byte sequence. One of the primary use cases for this		resulting byte sequence. One of the primary use cases for this
	thumbprint is as a naming scheme for identifying or selecting the		thumbprint is as a naming scheme for identifying or selecting the
	key, such as by using the COSE Key Thumbprint value as a "kid" (key		key, such as by using the COSE Key Thumbprint value as a "kid" (key
	ID). Another key use case involves key derivation functions that use		ID). Another key use case involves key derivation functions that use
	the thumbprints of public keys from the endpoints, along with other		the thumbprints of public keys from the endpoints, along with other
	application context information, to derive a symmetric key.		application context, to derive a symmetric key.
	This specification outlines how thumbprints of COSE Keys are		This specification outlines how thumbprints of COSE Keys are
	generated for both asymmetric and symmetric keys (see Sections 3 and		generated for both asymmetric and symmetric keys (see Sections 3 and
	4). Additionally, it introduces a new CBOR Web Token (CWT)		4). Additionally, it introduces a new CBOR Web Token (CWT)
	confirmation method, which has been added to the IANA "CWT		confirmation method, which has been added to the IANA "CWT
	Confirmation Methods" registry established by [RFC8747]. For further		Confirmation Methods" registry established by [RFC8747]. For further
	details on the use of a confirmation claim in a CWT with a proof-of-		details on the use of a confirmation claim in a CWT with a proof-of-
	possession key, refer to Section 3.1 of [RFC8747].		possession key, refer to Section 3.1 of [RFC8747].
	2. Terminology		2. Terminology
	skipping to change at line 221 ¶		skipping to change at line 221 ¶
	addition to the "kty" element, are required.		addition to the "kty" element, are required.
	5. Miscellaneous Considerations		5. Miscellaneous Considerations
	5.1. Why Not Include Optional COSE Key Parameters?		5.1. Why Not Include Optional COSE Key Parameters?
	Optional parameters of COSE Keys are intentionally not included in		Optional parameters of COSE Keys are intentionally not included in
	the COSE Key Thumbprint computation so that their absence or presence		the COSE Key Thumbprint computation so that their absence or presence
	in the COSE Key does not alter the resulting value. The COSE Key		in the COSE Key does not alter the resulting value. The COSE Key
	Thumbprint is a digest of the ordered essential parameters needed to		Thumbprint is a digest of the ordered essential parameters needed to
	represent a COSE, with all other parameters excluded.		represent a COSE Key, with all other parameters excluded.
	By excluding optional parameters, the COSE Key Thumbprint		By excluding optional parameters, the COSE Key Thumbprint
	consistently refers to the key itself, not to a key with additional		consistently refers to the key itself, not to a key with additional
	attributes. Different application contexts may include various		attributes. Different application contexts may include various
	optional attributes in the COSE Key structure. If these optional		optional attributes in the COSE Key structure. If these optional
	parameters were included in the thumbprint calculation, the resulting		parameters were included in the thumbprint calculation, the resulting
	values could differ for the same key depending on the attributes		values could differ for the same key depending on the attributes
	present. Including only the required parameters ensures that the		present. Including only the required parameters ensures that the
	COSE Key Thumbprint remains consistent for a given key, regardless of		COSE Key Thumbprint remains consistent for a given key, regardless of
	any additional attributes.		any additional attributes.
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