Keyed-Hash Message Authentication Code (HMAC)

Data Structures
struct	dtls_hmac_context_t

Macros
#define	DTLS_HMAC_BLOCKSIZE   64
#define	DTLS_HMAC_DIGEST_SIZE   32
#define	DTLS_HMAC_MAX   64

Enumerations
enum	dtls_hashfunc_t {   HASH_NONE =0, HASH_MD5 =1, HASH_SHA1 =2, HASH_SHA224 =3,   HASH_SHA256 =4, HASH_SHA384 =5, HASH_SHA512 =6 }

Functions
void	dtls_hmac_init (dtls_hmac_context_t *ctx, const unsigned char *key, size_t klen)
dtls_hmac_context_t *	dtls_hmac_new (const unsigned char *key, size_t klen)
void	dtls_hmac_free (dtls_hmac_context_t *ctx)
void	dtls_hmac_update (dtls_hmac_context_t *ctx, const unsigned char *input, size_t ilen)
int	dtls_hmac_finalize (dtls_hmac_context_t *ctx, unsigned char *result)

Detailed Description

NIST Standard FIPS 198 describes the Keyed-Hash Message Authentication Code (HMAC) which is used as hash function for the DTLS PRF.

Macro Definition Documentation

#define DTLS_HMAC_BLOCKSIZE   64

size of hmac blocks

Definition at line 73 of file hmac.h.

#define DTLS_HMAC_DIGEST_SIZE   32

digest size (for SHA-256)

Definition at line 74 of file hmac.h.

#define DTLS_HMAC_MAX   64

max number of bytes in digest

Definition at line 75 of file hmac.h.

Enumeration Type Documentation

enum dtls_hashfunc_t

List of known hash functions for use in dtls_hmac_init(). The identifiers are the same as the HashAlgorithm defined in Section 7.4.1.4.1 of RFC 5246.

Enumerator
HASH_NONE
HASH_MD5
HASH_SHA1
HASH_SHA224
HASH_SHA256
HASH_SHA384
HASH_SHA512

Definition at line 83 of file hmac.h.

Function Documentation

int dtls_hmac_finalize	(	dtls_hmac_context_t *	ctx,
		unsigned char *	result
	)

Completes the HMAC generation and writes the result to the given output parameter result. The buffer must be large enough to hold the message digest created by the actual hash function. If in doubt, use DTLS_HMAC_MAX. The function returns the number of bytes written to result.

Parameters

ctx	The HMAC context.
result	Output parameter where the MAC is written to.

Returns

Length of the MAC written to result.

Definition at line 127 of file hmac.c.

void dtls_hmac_free

(

dtls_hmac_context_t *

ctx

)

Releases the storage for ctx that has been allocated by dtls_hmac_new().

Parameters

ctx	The dtls_hmac_context_t to free.

Definition at line 121 of file hmac.c.

void dtls_hmac_init	(	dtls_hmac_context_t *	ctx,
		const unsigned char *	key,
		size_t	klen
	)

Initializes an existing HMAC context.

Parameters

ctx	The HMAC context to initialize.
key	The secret key.
klen	The length of key.

Definition at line 94 of file hmac.c.

dtls_hmac_context_t* dtls_hmac_new	(	const unsigned char *	key,
		size_t	klen
	)

Allocates a new HMAC context ctx with the given secret key. This function returns 1 if ctx has been set correctly, or 0 or -1 otherwise. Note that this function allocates new storage that must be released by dtls_hmac_free().

Parameters

key	The secret key.
klen	The length of key.

Returns

A new dtls_hmac_context_t object or NULL on error

Definition at line 83 of file hmac.c.

void dtls_hmac_update	(	dtls_hmac_context_t *	ctx,
		const unsigned char *	input,
		size_t	ilen
	)

Updates the HMAC context with data from input.

Parameters

ctx	The HMAC context.
input	The input data.
ilen	Size of input.

Definition at line 76 of file hmac.c.