Size of the key returned by get_short_circuit_kid().

It is always this size.

Definition at line 92 of file t_cose_util.h.

Create the hash of the to-be-signed (TBS) bytes for COSE.

Parameters

[in]	cose_alg_id	The COSE signing algorithm ID. Used to determine which hash function to use.
[in]	buffer_for_hash	Pointer and length of buffer into which the resulting hash is put.
[out]	hash	Pointer and length of the resulting hash.
[in]	protected_headers	The CBOR encoded protected headers.
[in]	payload	The CBOR encoded payload

Returns

This returns one of the error codes defined by t_cose_err_t.

Return values

T_COSE_ERR_SIG_STRUCT	Most likely this is because the protected_headers passed in is larger than T_COSE_SIGN1_MAX_PROT_HEADER.
T_COSE_ERR_UNSUPPORTED_HASH	If the hash algorithm is not known.
T_COSE_ERR_HASH_GENERAL_FAIL	In case of some general hash failure.

The input to the public key signature algorithm in COSE is the hash of a CBOR encoded structure containing the protected headers algorithm ID and a few other things. This formats that structure and computes the hash of it. These are known as the to-be-signed or "TBS" bytes.

Get the special kid for short-circuit signing.

Parameters

[in]	buffer_for_kid	Pointer and length of buffer into which the resulting hash is put. It should always be at least T_COSE_SHORT_CIRCUIT_KID_SIZE.
[out]	kid	Pointer and length of the returned kid.

Return values

T_COSE_SUCCESS	The kid was returned.
T_COSE_ERR_KEY_BUFFER_SIZE	buffer_for_kid is too small

This always returns the same key ID. It always indicates short-circuit signing. It is OK to hard code this as the probability of collision with this ID is extremely low and the same as for collision between any two key IDs (kids) of any sort.

This is the value of the kid.

   0xef, 0x95, 0x4b, 0x4b, 0xd9, 0xbd, 0xf6, 0x70,
   0xd0, 0x33, 0x60, 0x82, 0xf5, 0xef, 0x15, 0x2a,
   0xf8, 0xf3, 0x5b, 0x6a, 0x6c, 0x00, 0xef, 0xa6,
   0xa9, 0xa7, 0x1f, 0x49, 0x51, 0x7e, 0x18, 0xc6

Return hash algorithm ID from a signature algorithm ID.

Parameters

[in]

cose_sig_alg_id

A COSE signature algorithm identifier.

Returns

INT32_MAX when the signature algorithm ID is not known.

This works off of algorithm identifiers defined in the IANA COSE Registry. Corresponding local integer constants are defined in t_cose_defines.h.

COSE signing algorithms are the combination of public key algorithm, curve, key size, hash algorithm and hash size. They are simple integers making them convenient for direct use in code.

This function returns an identifier for only the hash algorithm from the combined identifier.

If the needed algorithm identifiers are not in the IANA registry, they can be added to it. This will take some time and work. It is also fine to use algorithms in the proprietary space.