Stateless helpers for the small subset of COSE used by EDHOC: COSE_Encrypt0 with AES-CCM* and COSE_Sign1 with ES256. More...

Functions
size_t	cose_encrypt0_seal (uint8_t alg, const uint8_t key, const uint8_t nonce, const uint8_t external_aad, size_t external_aad_len, uint8_t buf, size_t plaintext_len, size_t buf_capacity)
	AEAD-encrypt a buffer in place as a COSE_Encrypt0.
size_t	cose_encrypt0_open (uint8_t alg, const uint8_t key, const uint8_t nonce, const uint8_t external_aad, size_t external_aad_len, uint8_t buf, size_t ciphertext_len)
	AEAD-decrypt a buffer in place as a COSE_Encrypt0.
size_t	cose_sign1_sign (int8_t alg, const uint8_t private_key, const uint8_t protected_hdr, size_t protected_hdr_len, const uint8_t external_aad, size_t external_aad_len, const uint8_t payload, size_t payload_len, uint8_t *signature)
	Produce a COSE_Sign1 signature.
bool	cose_sign1_verify (int8_t alg, const uint8_t public_key, const uint8_t protected_hdr, size_t protected_hdr_len, const uint8_t external_aad, size_t external_aad_len, const uint8_t payload, size_t payload_len, const uint8_t *signature, size_t signature_len)
	Verify a COSE_Sign1 signature.
uint8_t	cose_get_key_len (uint8_t alg_id)
	Get the symmetric key length for a COSE AEAD algorithm.
uint8_t	cose_get_iv_len (uint8_t alg_id)
	Get the nonce/IV length for a COSE AEAD algorithm.
uint8_t	cose_get_tag_len (uint8_t alg_id)
	Get the authentication tag length for a COSE AEAD algorithm.

Detailed Description

Stateless helpers for the small subset of COSE used by EDHOC: COSE_Encrypt0 with AES-CCM* and COSE_Sign1 with ES256.

Function Documentation

◆ cose_encrypt0_open()

size_t cose_encrypt0_open	(	uint8_t	alg,
		const uint8_t *	key,
		const uint8_t *	nonce,
		const uint8_t *	external_aad,
		size_t	external_aad_len,
		uint8_t *	buf,
		size_t	ciphertext_len )

AEAD-decrypt a buffer in place as a COSE_Encrypt0.

Parameters

alg	COSE AEAD algorithm identifier.
key	Symmetric key (length implied by `alg`).
nonce	Nonce/IV (length implied by `alg`).
external_aad	CBOR-encoded external Additional Authenticated Data.
external_aad_len	Length of `external_aad` in bytes.
buf	In/out buffer; on entry holds plaintext \|\| tag, on return holds the recovered plaintext.
ciphertext_len	Length of plaintext \|\| tag in `buf`.

Returns: Plaintext length on success, 0 on failure (including authentication failure).

The protected header is treated as empty, matching how EDHOC uses COSE_Encrypt0.

Warning: Decryption happens in place before the tag is verified, so on failure (return 0) buf holds unauthenticated, attacker-influenced data. Callers must discard buf unless the return value is nonzero.

Definition at line 149 of file cose.c.

References cose_get_iv_len(), cose_get_key_len(), and cose_get_tag_len().

◆ cose_encrypt0_seal()

size_t cose_encrypt0_seal	(	uint8_t	alg,
		const uint8_t *	key,
		const uint8_t *	nonce,
		const uint8_t *	external_aad,
		size_t	external_aad_len,
		uint8_t *	buf,
		size_t	plaintext_len,
		size_t	buf_capacity )

AEAD-encrypt a buffer in place as a COSE_Encrypt0.

Parameters

alg	COSE AEAD algorithm identifier.
key	Symmetric key (length implied by `alg`).
nonce	Nonce/IV (length implied by `alg`).
external_aad	CBOR-encoded external Additional Authenticated Data.
external_aad_len	Length of `external_aad` in bytes.
buf	In/out buffer; on entry holds the plaintext, on return holds plaintext \|\| authentication tag.
plaintext_len	Length of the plaintext in `buf`.
buf_capacity	Total number of bytes available in `buf`. Must be at least `plaintext_len` plus the tag length for `alg`, or the call fails without writing the tag.

Returns: Total ciphertext length on success, 0 on failure.

The protected header is treated as empty, matching how EDHOC uses COSE_Encrypt0. The Enc_structure built internally is [ "Encrypt0", h'', external_aad ].

Definition at line 103 of file cose.c.

References cose_get_iv_len(), cose_get_key_len(), and cose_get_tag_len().

◆ cose_get_iv_len()

uint8_t cose_get_iv_len ( uint8_t alg_id )

Get the nonce/IV length for a COSE AEAD algorithm.

Parameters

alg_id COSE algorithm identifier.

Returns: IV length in bytes, 0 if the algorithm is unknown.

Definition at line 294 of file cose.c.

Referenced by cose_encrypt0_open(), and cose_encrypt0_seal().

◆ cose_get_key_len()

uint8_t cose_get_key_len ( uint8_t alg_id )

Get the symmetric key length for a COSE AEAD algorithm.

Parameters

alg_id COSE algorithm identifier.

Returns: Key length in bytes, 0 if the algorithm is unknown.

Definition at line 280 of file cose.c.

Referenced by cose_encrypt0_open(), and cose_encrypt0_seal().

◆ cose_get_tag_len()

uint8_t cose_get_tag_len ( uint8_t alg_id )

Get the authentication tag length for a COSE AEAD algorithm.

Parameters

alg_id COSE algorithm identifier.

Returns: Tag length in bytes, 0 if the algorithm is unknown.

Definition at line 308 of file cose.c.

Referenced by cose_encrypt0_open(), and cose_encrypt0_seal().

◆ cose_sign1_sign()

size_t cose_sign1_sign	(	int8_t	alg,
		const uint8_t *	private_key,
		const uint8_t *	protected_hdr,
		size_t	protected_hdr_len,
		const uint8_t *	external_aad,
		size_t	external_aad_len,
		const uint8_t *	payload,
		size_t	payload_len,
		uint8_t *	signature )

Produce a COSE_Sign1 signature.

Parameters

alg	Signing algorithm identifier (only `ES256` is supported).
private_key	ECDSA private key.
protected_hdr	CBOR-encoded protected header bytes.
protected_hdr_len	Length of `protected_hdr`.
external_aad	CBOR-encoded external Additional Authenticated Data.
external_aad_len	Length of `external_aad`.
payload	Payload bytes to sign.
payload_len	Length of `payload`.
signature	Output buffer for the signature (`P256_SIGNATURE_LEN` bytes for ES256).

Returns: Signature length on success, 0 on failure.

Definition at line 209 of file cose.c.

References ecc_sign_hash(), and P256_SIGNATURE_LEN.

Referenced by edhoc_generate_message_2(), and edhoc_generate_message_3().

◆ cose_sign1_verify()

bool cose_sign1_verify	(	int8_t	alg,
		const uint8_t *	public_key,
		const uint8_t *	protected_hdr,
		size_t	protected_hdr_len,
		const uint8_t *	external_aad,
		size_t	external_aad_len,
		const uint8_t *	payload,
		size_t	payload_len,
		const uint8_t *	signature,
		size_t	signature_len )

Verify a COSE_Sign1 signature.

Parameters

alg	Signing algorithm identifier (only `ES256` is supported).
public_key	ECDSA public key (`2` * `ECC_KEY_LEN` bytes for ES256).
protected_hdr	CBOR-encoded protected header bytes.
protected_hdr_len	Length of `protected_hdr`.
external_aad	CBOR-encoded external Additional Authenticated Data.
external_aad_len	Length of `external_aad`.
payload	Payload bytes that were signed.
payload_len	Length of `payload`.
signature	Signature to verify.
signature_len	Length of `signature`.

Returns: true on a valid signature, false otherwise.

Definition at line 242 of file cose.c.

References ecc_verify_hash(), and P256_SIGNATURE_LEN.

Referenced by edhoc_authenticate_msg().

Functions

Detailed Description

Function Documentation

◆ cose_encrypt0_open()

◆ cose_encrypt0_seal()

◆ cose_get_iv_len()

◆ cose_get_key_len()

◆ cose_get_tag_len()

◆ cose_sign1_sign()

◆ cose_sign1_verify()