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