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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" PKCS5_PBKDF2_HMAC, PKCS5_PBKDF2_HMAC_SHA1 \- password based derivation routines with salt and iteration count .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #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); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\s-1\fBPKCS5_PBKDF2_HMAC\s0()\fR derives a key from a password using a salt and iteration count as specified in \s-1RFC 2898.\s0 .PP \&\fBpass\fR is the password used in the derivation of length \fBpasslen\fR. \fBpass\fR is an optional parameter and can be \s-1NULL.\s0 If \fBpasslen\fR is \-1, then the function will calculate the length of \fBpass\fR using \fBstrlen()\fR. .PP \&\fBsalt\fR is the salt used in the derivation of length \fBsaltlen\fR. If the \&\fBsalt\fR is \s-1NULL,\s0 then \fBsaltlen\fR must be 0. The function will not attempt to calculate the length of the \fBsalt\fR because it is not assumed to be \s-1NULL\s0 terminated. .PP \&\fBiter\fR is the iteration count and its value should be greater than or equal to 1. \s-1RFC 2898\s0 suggests an iteration count of at least 1000. Any \&\fBiter\fR less than 1 is treated as a single iteration. .PP \&\fBdigest\fR is the message digest function used in the derivation. Values include any of the EVP_* message digests. \s-1\fBPKCS5_PBKDF2_HMAC_SHA1\s0()\fR calls \&\s-1\fBPKCS5_PBKDF2_HMAC\s0()\fR with \fBEVP_sha1()\fR. .PP The derived key will be written to \fBout\fR. The size of the \fBout\fR buffer is specified via \fBkeylen\fR. .SH "NOTES" .IX Header "NOTES" A typical application of this function is to derive keying material for an encryption algorithm from a password in the \fBpass\fR, a salt in \fBsalt\fR, and an iteration count. .PP Increasing the \fBiter\fR 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. .PP These functions make no assumption regarding the given password. It will simply be treated as a byte sequence. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\s-1\fBPKCS5_PBKDF2_HMAC\s0()\fR and \s-1\fBPBKCS5_PBKDF2_HMAC_SHA1\s0()\fR return 1 on success or 0 on error. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBevp\fR\|(7), \fBRAND_bytes\fR\|(3), \&\fBEVP_BytesToKey\fR\|(3), \&\fBpassphrase\-encoding\fR\|(7) .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2014\-2018 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.