1=pod 2 3=head1 NAME 4 5PKCS5_PBKDF2_HMAC, PKCS5_PBKDF2_HMAC_SHA1 - password based derivation routines with salt and iteration count 6 7=head1 SYNOPSIS 8 9 #include <openssl/evp.h> 10 11 int PKCS5_PBKDF2_HMAC(const char *pass, int passlen, 12 const unsigned char *salt, int saltlen, int iter, 13 const EVP_MD *digest, 14 int keylen, unsigned char *out); 15 16 int PKCS5_PBKDF2_HMAC_SHA1(const char *pass, int passlen, 17 const unsigned char *salt, int saltlen, int iter, 18 int keylen, unsigned char *out); 19 20=head1 DESCRIPTION 21 22PKCS5_PBKDF2_HMAC() derives a key from a password using a salt and iteration count 23as specified in RFC 2898. 24 25B<pass> is the password used in the derivation of length B<passlen>. B<pass> 26is an optional parameter and can be NULL. If B<passlen> is -1, then the 27function will calculate the length of B<pass> using strlen(). 28 29B<salt> is the salt used in the derivation of length B<saltlen>. If the 30B<salt> is NULL, then B<saltlen> must be 0. The function will not 31attempt to calculate the length of the B<salt> because it is not assumed to 32be NULL terminated. 33 34B<iter> is the iteration count and its value should be greater than or 35equal to 1. RFC 2898 suggests an iteration count of at least 1000. Any 36B<iter> value less than 1 is invalid; such values will result in failure 37and raise the PROV_R_INVALID_ITERATION_COUNT error. 38 39B<digest> is the message digest function used in the derivation. 40PKCS5_PBKDF2_HMAC_SHA1() calls PKCS5_PBKDF2_HMAC() with EVP_sha1(). 41 42The derived key will be written to B<out>. The size of the B<out> buffer 43is specified via B<keylen>. 44 45=head1 NOTES 46 47A typical application of this function is to derive keying material for an 48encryption algorithm from a password in the B<pass>, a salt in B<salt>, 49and an iteration count. 50 51Increasing the B<iter> parameter slows down the algorithm which makes it 52harder for an attacker to perform a brute force attack using a large number 53of candidate passwords. 54 55These functions make no assumption regarding the given password. 56It will simply be treated as a byte sequence. 57 58=head1 RETURN VALUES 59 60PKCS5_PBKDF2_HMAC() and PBKCS5_PBKDF2_HMAC_SHA1() return 1 on success or 0 on error. 61 62=head1 SEE ALSO 63 64L<evp(7)>, L<RAND_bytes(3)>, 65L<EVP_BytesToKey(3)>, 66L<passphrase-encoding(7)> 67 68=head1 COPYRIGHT 69 70Copyright 2014-2021 The OpenSSL Project Authors. All Rights Reserved. 71 72Licensed under the Apache License 2.0 (the "License"). You may not use 73this file except in compliance with the License. You can obtain a copy 74in the file LICENSE in the source distribution or at 75L<https://www.openssl.org/source/license.html>. 76 77=cut 78
