RFC 8152: CBOR Object Signing and Encryption (COSE) - RFC … COSE_MAC0 is used when a recipient structure is not needed because the key to be used is implicitly known. COSE_MAC is used for all other cases. These include a requirement for multiple recipients, the key being unknown, and a recipient algorithm of other than direct. In this section, we describe the structure and methods to be used when doing MAC authentication in COSE. …