On Sun, May 28, 2023 at 05:23:11PM +0200, Hannes Tschofenig wrote: > I agree regarding OKP and HSS-LMS key types, Ilari. > > Kohei and I wanted to get an initial version out to the group to see > what others in the group think. Hence, we kept is short & simple. >
Some (bad) attempt at text (edited from text in the draft, needs further editing): 3. COSE Key Thumbprint The thumbprint of a COSE Key MUST be computed as follows: 1. Construct a COSE_Key structure (see Section 7 of [RFC9052]) containing only the required parmeters representing the key. This specification describes what those required parameters are and what, if necessary, the data types are. 2. Encode the COSE_Key into byte string using the Core Deterministic Encoding described in Section 4.2.1 of [RFC8949]. 3. Hash the bytes from step (2) with a cryptographic hash function H. For example, SHA-256 [RFC6234] may be used as a hash function. The resulting value is the COSE Key Thumbprint with H of the COSE_Key. The details of this computation are further described in subsequent sections. 4. Required COSE Key Parameters Only the public key parameters of a key's representation are used when computing its COSE Key Thumbprint value. This section summarizes these parameters. The "kty" (label: 1) parameter MUST be present for all key types and the values found in the IANA COSE Key Types registry MUST be used. Other parameters depend on the key type. The subsection below list the required parameters for commonly used key types (in order). 4.1. OKP OKP keys (value: 1) have the following parameters: * "kty" label: 1 value: 1 * "crv" label: -1 value: int/tstr * "x" label: -2 value: bstr 4.2. EC2 EC2 keys (value: 2) have the following parameters: * "kty" label: 1 value: 2 * "crv" label: -1 value: int/tstr * "x" label: -2 value: bstr * "y" label: -3 value: bstr Note that for interoperability, uncompressed representation MUST be used. Hence, the parameter "y" is bstr. A compressed key representation MUST be decompressed before thumbprint calculation. 4.3. RSA RSA keys (value: 3) have the following parameters: * "kty" label: 1 value: 3 * "n" label: -1 value: bstr * "e" label: -2 value: bstr 4.4. Symmetric Symmetric keys do not have thumbprints. 4.5. HSS-LMS HSS-LMS keys (value: 5) have the following parameters: * "kty" label: 1 value: 5 * "pub" label: -1 value: bstr -Ilari _______________________________________________ COSE mailing list [email protected] https://www.ietf.org/mailman/listinfo/cose
