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.\" $OpenBSD: pkcs5_pbkdf2.3,v 1.5 2013/06/05 03:40:26 tedu Exp $
.\"
.\" Copyright (c) 2012 Ted Unangst <tedu@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: June 5 2013 $
.Dt PKCS5_PBKDF2 3
.Os
.Sh NAME
.Nm pkcs5_pbkdf2
.Nd password-based key derivation function
.Sh SYNOPSIS
.In util.h
.Ft int
.Fn pkcs5_pbkdf2 "const char *pass" "size_t pass_len" "const char *salt" \
"size_t salt_len" "u_int8_t *key" "size_t key_len" "u_int rounds"
.Sh DESCRIPTION
The
.Nm
function converts a password into a byte array suitable for use as
an encryption key.
The password and salt values are combined and repeatedly hashed
.Ar rounds
times.
The salt value should be randomly generated beforehand.
The repeated hashing is designed to thwart discovery of the key via
password guessing attacks.
The higher the number of rounds, the slower each attempt will be.
A minimum value of at least 1000 is recommended.
.Sh RETURN VALUES
The
.Fn pkcs5_pbkdf2
function returns 0 to indicate success and -1 for failure.
.\" .Sh EXAMPLES
.\" .Sh ERRORS
.Sh SEE ALSO
.Xr sha1 1 ,
.Xr bcrypt_pbkdf 3
.Sh STANDARDS
.Rs
.%A B. Kaliski
.%D September 2000
.%R RFC 2898
.%T PKCS #5: Password-Based Cryptography Specification Version 2.0
.Re
.\" .Sh HISTORY
.\" .Sh AUTHORS
.Sh CAVEATS
The standard allows for different hash functions to be used.
This implementation only uses
.Xr sha1 1 .
.\" .Sh BUGS
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