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PKCS5_PBKDF2_HMAC documentation submitted by Jeffrey Walton
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=pod | ||
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=head1 NAME | ||
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PKCS5_PBKDF2_HMAC - password based derivation routine with salt and iteration count | ||
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=head1 SYNOPSIS | ||
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#include <openssl/evp.h> | ||
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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); | ||
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=head1 DESCRIPTION | ||
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PKCS5_PBKDF2_HMAC() derives a key from a password using a salt and iteration count | ||
as specified in RFC 2898. | ||
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B<pass> is the password used in the derivation of length B<passlen>. B<pass> | ||
is an optional parameter and can be NULL. If B<passlen> is -1, then the | ||
function will calculate the length of B<pass> using strlen(). | ||
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B<salt> is the salt used in the derivation of length B<saltlen>. If the | ||
B<salt> is NULL, then B<saltlen> must be 0. The function will not | ||
attempt to calculate the length of the B<salt> because its not assumed to | ||
be NULL terminated. | ||
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B<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 | ||
B<iter> less than 1 is treated as a single iteration. | ||
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B<digest> is 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(). | ||
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The derived key will be written to B<out>. The size of the B<out> buffer | ||
is specified via B<keylen>. | ||
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=head1 NOTES | ||
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A typical application of this function is to derive keying material for an | ||
encryption algorithm from a password in the B<pass>, a salt in B<salt>, | ||
and an iteration count. | ||
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Increasing the B<iter> parameter slows down the algorithm which makes it | ||
harder for an attacker to peform a brute force attack using a large number | ||
of candidate passwords. | ||
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=head1 RETURN VALUES | ||
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PKCS5_PBKDF2_HMAC() returns 1 on success or 0 on error. | ||
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=head1 SEE ALSO | ||
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L<evp(3)|evp(3)>, L<rand(3)|rand(3)>, | ||
L<EVP_BytesToKey(3)|EVP_BytesToKey(3)> | ||
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=head1 HISTORY | ||
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=cut |