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.\" $OpenBSD: PKCS5_PBKDF2_HMAC.3,v 1.4 2016/11/28 23:27:55 schwarze Exp $
.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Jeffrey Walton <noloader@gmail.com>.
.\" Copyright (c) 2014, 2015 The OpenSSL Project. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\"
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in
.\" the documentation and/or other materials provided with the
.\" distribution.
.\"
.\" 3. All advertising materials mentioning features or use of this
.\" software must display the following acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\" endorse or promote products derived from this software without
.\" prior written permission. For written permission, please contact
.\" openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\" nor may "OpenSSL" appear in their names without prior written
.\" permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\" acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: November 28 2016 $
.Dt PKCS5_PBKDF2_HMAC 3
.Os
.Sh NAME
.Nm PKCS5_PBKDF2_HMAC ,
.Nm PKCS5_PBKDF2_HMAC_SHA1
.Nd password based derivation routines with salt and iteration count
.Sh SYNOPSIS
.In openssl/evp.h
.Ft int
.Fo PKCS5_PBKDF2_HMAC
.Fa "const char *pass"
.Fa "int passlen"
.Fa "const unsigned char *salt"
.Fa "int saltlen"
.Fa "int iter"
.Fa "const EVP_MD *digest"
.Fa "int keylen"
.Fa "unsigned char *out"
.Fc
.Ft int
.Fo PKCS5_PBKDF2_HMAC_SHA1
.Fa "const char *pass"
.Fa "int passlen"
.Fa "const unsigned char *salt"
.Fa "int saltlen"
.Fa "int iter"
.Fa "int keylen"
.Fa "unsigned char *out"
.Fc
.Sh DESCRIPTION
.Fn PKCS5_PBKDF2_HMAC
derives a key from a password using a salt and iteration count as
specified in RFC 2898.
.Pp
.Fa pass
is the password used in the derivation of length
.Fa passlen .
.Fa pass
is an optional parameter and can be
.Dv NULL .
If
.Fa passlen
is -1, then the function will calculate the length of
.Fa pass
using
.Xr strlen 3 .
.Pp
.Fa salt
is the salt used in the derivation of length
.Fa saltlen .
If the
.Fa salt
is
.Dv NULL ,
then
.Fa saltlen
must be 0.
The function will not attempt to calculate the length of the
.Fa salt
because it is not assumed to be NUL terminated.
.Pp
.Fa iter
is the iteration count and its value should be greater than or equal to 1.
RFC 2898 suggests an iteration count of at least 1000.
Any
.Fa iter
less than 1 is treated as a single iteration.
.Pp
.Fa digest
is the message digest function used in the derivation.
Values include any of the EVP_* message digests.
.Fn PKCS5_PBKDF2_HMAC_SHA1
calls
.Fn PKCS5_PBKDF2_HMAC
with
.Xr EVP_sha1 3 .
.Pp
The derived key will be written to
.Fa out .
The size of the
.Fa out
buffer is specified via
.Fa keylen .
.Pp
A typical application of this function is to derive keying material for
an encryption algorithm from a password in the
.Fa pass ,
a salt in
.Fa salt ,
and an iteration count.
.Pp
Increasing the
.Fa iter
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.
.Sh RETURN VALUES
.Fn PKCS5_PBKDF2_HMAC
and
.Fn PBKCS5_PBKDF2_HMAC_SHA1
return 1 on success or 0 on error.
.Sh SEE ALSO
.Xr evp 3 ,
.Xr EVP_BytesToKey 3 ,
.Xr RAND_bytes 3
|
