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.\" ========================================================================
.\"
.IX Title "PKCS5_PBKDF2_HMAC 3"
.TH PKCS5_PBKDF2_HMAC 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.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>.