gnutls_prf (3) - Linux Manuals

gnutls_prf: API function


gnutls_prf - API function


#include <gnutls/gnutls.h>

int gnutls_prf(gnutls_session_t session, size_t label_size, const char * label, int server_random_first, size_t extra_size, const char * extra, size_t outsize, char * out);


gnutls_session_t session
is a gnutls_session_t structure.
size_t label_size
length of the label variable.
const char * label
label used in PRF computation, typically a short string.
int server_random_first
non-zero if server random field should be first in seed
size_t extra_size
length of the extra variable.
const char * extra
optional extra data to seed the PRF with.
size_t outsize
size of pre-allocated output buffer to hold the output.
char * out
pre-allocated buffer to hold the generated data.


Applies the TLS Pseudo-Random-Function (PRF) on the master secret and the provided data, seeded with the client and server random fields.

The output of this function is identical to RFC5705 extractor if extra and extra_size are set to zero. Otherwise, extra should contain the context value prefixed by a two-byte length.

The label variable usually contains a string denoting the purpose for the generated data. The server_random_first indicates whether the client random field or the server random field should be first in the seed. Non-zero indicates that the server random field is first, 0 that the client random field is first.

The extra variable can be used to add more data to the seed, after the random variables. It can be used to make sure the generated output is strongly connected to some additional data (e.g., a string used in user authentication).

The output is placed in out , which must be pre-allocated.


GNUTLS_E_SUCCESS on success, or an error code.


Report bugs to <bugs [at]>.
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