



@deftypefun {void} {gnutls_srp_set_server_fake_salt_seed} (gnutls_srp_server_credentials_t @var{cred}, const gnutls_datum_t * @var{seed}, unsigned int @var{salt_length})
@var{cred}: is a @code{gnutls_srp_server_credentials_t}  structure

@var{seed}: is the seed data, only needs to be valid until the function
returns; size of the seed must be greater than zero

@var{salt_length}: is the length of the generated fake salts

This function sets the seed that is used to generate salts for
invalid (non-existent) usernames.

In order to prevent attackers from guessing valid usernames,
when a user does not exist gnutls generates a salt and a verifier
and proceeds with the protocol as usual.
The authentication will ultimately fail, but the client cannot tell
whether the username is valid (exists) or invalid.

If an attacker learns the seed, given a salt (which is part of the
handshake) which was generated when the seed was in use, it can tell
whether or not the authentication failed because of an unknown username.
This seed cannot be used to reveal application data or passwords.

 @code{salt_length} should represent the salt length your application uses.
Generating fake salts longer than 20 bytes is not supported.

By default the seed is a random value, different each time a
@code{gnutls_srp_server_credentials_t}  is allocated and fake salts are
16 bytes long.

@strong{Since:} 3.3.0
@end deftypefun
