LIBKECCAK_HMAC_DIGEST(3)

NAME
libkeccak_hmac_digest - Complete the HMAC-hashing of a message with erasure

SYNOPSIS
#include <libkeccak.h>
int libkeccak_hmac_digest(struct libkeccak_hmac_state *state, const void *msg, size_t msglen,
                          size_t bits, const char *suffix, void *hashsum);

Link with -lkeccak.

DESCRIPTION
The libkeccak_hmac_digest() function absorbes the last part of (or all of) a message, and returns the HMAC hash of the entire message. The last part of the message is specified by the msg parameter, and its byte-size is specified by the msglen parameter. If all of the message has already be processed by calls to the libkeccak_hmac_update(3) function or the libkeccak_hmac_fast_update(3) function (with the same pointer on state,) msg and msglen should be set to NULL and 0, respectively.

If the message is not comprised a whole number of bytes, the number of bits, modulus 8, in the message should be specified in the bits parameter. msglen must only count the number of whole bytes, that is, the floor of the number of bits in the message divided by 8.

suffix should be a NUL-terminated string of ASCII '1':s and '0':s, representing the bits that should be appended to the message. If this string is empty, NULL may be used instead. This is used to select hash algorithm. For pure Keccak, NULL or "" is used. For the other algorithms the constants LIBKECCAK_SHA3_SUFFIX (for SHA-3), LIBKECCAK_RAWSHAKE_SUFFIX (for RawSHAKE), and LIBKECCAK_SHAKE_SUFFIX (for SHAKE) are used.

The hash of the message will be stored to hashsum, unless hashsum is NULL (which increases the performance of the call.) A total of ((state->n + 7) / 8) bytes will be written to the beginning of hashsum. Therefore, hashsum needs at least an allocation size of that number of bytes.

The libkeccak_hmac_digest() function may reallocate the state's message chunk buffer. When doing so, it attempts to do so as securely as possible, rather than as fast as possible.

RETURN VALUES
The libkeccak_hmac_digest() function returns 0 upon successful completion. On error, -1 is returned and errno is set to describe the error.

ERRORS
The libkeccak_hmac_digest() function may fail for any reason specified by the function malloc(3).

SEE ALSO
libkeccak_hmac_create(3), libkeccak_hmac_initialise(3), libkeccak_hmac_update(3), libkeccak_hmac_fast_digest(3)