213 lines
5.9 KiB
Groff
213 lines
5.9 KiB
Groff
.\" $NetBSD: sha1.3,v 1.3 1999/02/28 00:00:03 ross Exp $
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.\" $OpenBSD: sha1.3,v 1.9 1998/03/07 22:18:12 millert Exp $
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.\"
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.\" Copyright (c) 1997 Todd C. Miller <Todd.Miller@courtesan.com>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Todd C. Miller.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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.\" AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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.\" THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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.\" EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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.\" PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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.\" OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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.\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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.\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" See http://csrc.nist.gov/fips/fip180-1.txt for the detailed standard
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.\"
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.Dd July 10, 1997
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.Dt SHA1 3
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.Sh NAME
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.Nm SHA1Init ,
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.Nm SHA1Update ,
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.Nm SHA1Final ,
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.Nm SHA1Transform ,
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.Nm SHA1End ,
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.Nm SHA1File ,
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.Nm SHA1Data
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.Nd calculate the NIST Secure Hash Algorithm
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sha1.h>
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.Ft void
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.Fn SHA1Init "SHA1_CTX *context"
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.Ft void
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.Fn SHA1Update "SHA1_CTX *context" "const u_char *data" "u_int len"
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.Ft void
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.Fn SHA1Final "u_char digest[20]" "SHA1_CTX *context"
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.Ft void
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.Fn SHA1Transform "u_int32_t state[5]" "u_char buffer[64]"
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.Ft "char *"
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.Fn SHA1End "SHA1_CTX *context" "char *buf"
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.Ft "char *"
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.Fn SHA1File "char *filename" "char *buf"
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.Ft "char *"
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.Fn SHA1Data "u_char *data" "u_int len" "char *buf"
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.Sh DESCRIPTION
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The SHA1 functions implement the NIST Secure Hash Algorithm (SHA-1),
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FIPS PUB 180-1. SHA-1 is used to generate a condensed representation
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of a message called a message digest. The algorithm takes a
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message less than 2^64 bits as input and produces a 160-bit digest
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suitable for use as a digital signature.
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.Pp
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The SHA1 functions are considered to be more secure than the
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.Xr md4 3
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and
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.Xr md5 3
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functions with which they share a similar interface.
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.Pp
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The
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.Fn SHA1Init
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function initializes a SHA1_CTX
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.Ar context
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for use with
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.Fn SHA1Update ,
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and
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.Fn SHA1Final .
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The
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.Fn SHA1Update
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function adds
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.Ar data
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of length
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.Ar len
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to the SHA1_CTX specified by
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.Ar context.
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.Fn SHA1Final
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is called when all data has been added via
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.Fn SHA1Update
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and stores a message digest in the
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.Ar digest
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parameter.
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When a null pointer is passed to
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.Fn SHA1Final
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as first argument only the final padding will be applied and the
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current context can still be used with
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.Fn SHA1Update .
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.Pp
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The
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.Fn SHA1Transform
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function is used by
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.Fn SHA1Update
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to hash 512-bit blocks and forms the core of the algorithm.
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Most programs should use the interface provided by
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.Fn SHA1Init ,
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.Fn SHA1Update
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and
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.Fn SHA1Final
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instead of calling
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.Fn SHA1Transform
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directly.
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.Pp
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The
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.Fn SHA1End
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function is a front end for
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.Fn SHA1Final
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which converts the digest into an
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.Tn ASCII
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representation of the 160 bit digest in hexadecimal.
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.Pp
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The
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.Fn SHA1File
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function calculates the digest for a file and returns the result via
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.Fn SHA1End .
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If
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.Fn SHA1File
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is unable to open the file a NULL pointer is returned.
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.Pp
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The
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.Fn SHA1Data
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function
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calculates the digest of an arbitrary string and returns the result via
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.Fn SHA1End .
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.Pp
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For each of the
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.Fn SHA1End ,
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.Fn SHA1File ,
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and
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.Fn SHA1Data
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functions the
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.Ar buf
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parameter should either be a string of at least 41 characters in
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size or a NULL pointer. In the latter case, space will be dynamically
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allocated via
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.Xr malloc 3
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and should be freed using
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.Xr free 3
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when it is no longer needed.
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.Sh EXAMPLES
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The follow code fragment will calculate the digest for
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the string "abc" which is ``0xa9993e36476816aba3e25717850c26c9cd0d89d''.
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.Bd -literal -offset indent
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SHA1_CTX sha;
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u_char results[20];
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char *buf;
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int n;
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buf = "abc";
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n = strlen(buf);
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SHA1Init(&sha);
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SHA1Update(&sha, (u_char *)buf, n);
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SHA1Final(results, &sha);
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/* Print the digest as one long hex value */
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printf("0x");
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for (n = 0; n < 20; n++)
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printf("%x", results[n]);
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putchar('\\n');
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.Ed
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.Pp
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Alternately, the helper functions could be used in the following way:
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.Bd -literal -offset indent
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SHA1_CTX sha;
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u_char output[41];
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char *buf = "abc";
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printf("0x%s", SHA1Data(buf, strlen(buf), output));
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.Ed
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.Sh CAVEATS
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This implementation of SHA-1 has not been validated by NIST
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and as such is not in official compliance with the standard.
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.Pp
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If a message digest is to be copied to a multi-byte type (ie:
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an array of five 32-bit integers) it will be necessary to
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perform byte swapping on little endian machines such as the i386, alpha,
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and vax.
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.Sh AUTHOR
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This implementation of SHA-1 was written by Steve Reid.
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.br
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The
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.Fn SHA1End ,
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.Fn SHA1File ,
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and
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.Fn SHA1Data
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helper functions are derived from code written by Poul-Henning Kamp.
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.Sh SEE ALSO
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.\" .Xr sha1 1 ,
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.Xr md5 1 ,
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.Xr md4 3 ,
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.Xr md5 3
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.Pp
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.Rs
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.%A J. Burrows
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.%T The Secure Hash Standard
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.%O FIPS PUB 180-1
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.Re
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.Sh HISTORY
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The SHA-1 functions appeared in OpenBSD 2.0.
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