HMAC, HMAC_CTX_init, HMAC_Init, HMAC_Init_ex, HMAC_Update, HMAC_Final,
HMAC_CTX_cleanup, HMAC_cleanup - HMAC message authentication code
unsigned char *HMAC(const EVP_MD *evp_md, const void *key,
int key_len, const unsigned char *d, int n,
unsigned char *md, unsigned int *md_len);
void HMAC_CTX_init(HMAC_CTX *ctx);
int HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
const EVP_MD *md);
int HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int key_len,
const EVP_MD *md, ENGINE *impl);
int HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len);
int HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len);
void HMAC_CTX_cleanup(HMAC_CTX *ctx);
void HMAC_cleanup(HMAC_CTX *ctx);
HMAC is a MAC (message authentication code), i.e. a keyed hash function used for
message authentication, which is based on a hash function.
computes the message authentication code of the n
using the hash function evp_md
and the key key
It places the result in md
(which must have space for the output of the
hash function, which is no more than EVP_MAX_MD_SIZE
is NULL, the digest is placed in a static array. The size of the
output is placed in md_len
, unless it is NULL
can be EVP_sha1()
initialises a HMAC_CTX
before first use. It must
erases the key and other data from the HMAC_CTX
and releases any associated resources. It must be called when an
is no longer required.
is an alias for HMAC_CTX_cleanup()
back compatibility with 0.9.6b, it is deprecated.
The following functions may be used if the message is not completely stored in
initializes a HMAC_CTX
structure to use the hash
and the key key
which is key_len
long. It is deprecated and only included for backward compatibility with
initializes or reuses a HMAC_CTX
structure to use
the hash function evp_md
and key key
. If both are NULL (or
is the same as the previous digest used by ctx
is NULL) the existing key is reused. ctx
must have been
created with HMAC_CTX_new()
before the first use of an HMAC_CTX
in this function. N.B. HMAC_Init() had this
undocumented behaviour in previous versions of OpenSSL - failure to
switch to HMAC_Init_ex() in programs that expect
it will cause them to stop working
NB: if HMAC_Init_ex() is called with key
NULL and evp_md is not the same as the previous digest
used by ctx then an error is returned because reuse of
an existing key with a different digest is not supported.
can be called repeatedly with chunks of the message to be
authenticated ( len
bytes at data
places the message authentication code in md
must have space for the hash function output.
returns a pointer to the message authentication code or NULL if an
return 1 for
success or 0 if an error occurred.
do not return values.
are available since SSLeay 0.9.0.
available since OpenSSL 0.9.7.
return values in versions of OpenSSL before 1.0.0.