NAME
PKCS5_PBKDF2_HMAC,
PKCS5_PBKDF2_HMAC_SHA1 —
password based derivation routines with
salt and iteration count
SYNOPSIS
#include
<openssl/evp.h>
int
PKCS5_PBKDF2_HMAC(const char
*pass, int passlen, const
unsigned char *salt, int saltlen,
int iter, const EVP_MD *digest,
int keylen, unsigned char
*out);
int
PKCS5_PBKDF2_HMAC_SHA1(const char
*pass, int passlen, const
unsigned char *salt, int saltlen,
int iter, int keylen,
unsigned char *out);
DESCRIPTION
PKCS5_PBKDF2_HMAC()
derives a key from a password using a salt and iteration count as specified
in RFC 2898.
pass is the password used in the derivation
of length passlen. pass is an
optional parameter and can be NULL. If
passlen is -1, then the function will calculate the
length of pass using
strlen(3).
salt is the salt used in the derivation of
length saltlen. If the salt is
NULL, then saltlen must be 0.
The function will not attempt to calculate the length of the
salt because it is not assumed to be NUL
terminated.
iter is the iteration count and its value should be greater than or equal to 1. RFC 2898 suggests an iteration count of at least 1000. Any iter less than 1 is treated as a single iteration.
digest is the
message digest function used in the derivation. Values include any of the
EVP_* message digests.
PKCS5_PBKDF2_HMAC_SHA1()
calls PKCS5_PBKDF2_HMAC() with
EVP_sha1(3).
The derived key will be written to out. The size of the out buffer is specified via keylen.
A typical application of this function is to derive keying material for an encryption algorithm from a password in the pass, a salt in salt, and an iteration count.
Increasing the iter parameter slows down the algorithm which makes it harder for an attacker to perform a brute force attack using a large number of candidate passwords.
RETURN VALUES
PKCS5_PBKDF2_HMAC() and
PBKCS5_PBKDF2_HMAC_SHA1() return 1 on success or 0
on error.
SEE ALSO
HISTORY
PKCS5_PBKDF2_HMAC_SHA1() first appeared in
OpenSSL 0.9.4 and has been available since OpenBSD
2.6.
PKCS5_PBKDF2_HMAC() first appeared in
OpenSSL 1.0.0 and has been available since OpenBSD
4.9.