\"      $NetBSD: sha1.3,v 1.9 2018/11/27 10:38:14 wiz Exp $
\"      $OpenBSD: sha1.3,v 1.9 1998/03/07 22:18:12 millert Exp $
\"
\" Copyright (c) 1997, 2004 Todd C. Miller <[email protected]>
\"
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\" purpose with or without fee is hereby granted, provided that the above
\" copyright notice and this permission notice appear in all copies.
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\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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\" See http://csrc.nist.gov/fips/fip180-1.txt for the detailed standard
\"
Dd November 27, 2018
Dt SHA1 3
Os
Sh NAME
Nm SHA1Init ,
Nm SHA1Update ,
Nm SHA1Final ,
Nm SHA1Transform ,
Nm SHA1End ,
Nm SHA1File ,
Nm SHA1FileChunk ,
Nm SHA1Data
Nd calculate the NIST Secure Hash Algorithm
Sh SYNOPSIS
In sys/types.h
In sha1.h
Ft void
Fn SHA1Init "SHA1_CTX *context"
Ft void
Fn SHA1Update "SHA1_CTX *context" "const uint8_t *data" "u_int len"
Ft void
Fn SHA1Final "uint8_t digest[20]" "SHA1_CTX *context"
Ft void
Fn SHA1Transform "uint32_t state[5]" "uint8_t buffer[64]"
Ft "char *"
Fn SHA1End "SHA1_CTX *context" "char *buf"
Ft "char *"
Fn SHA1File "char *filename" "char *buf"
Ft "char *"
Fn SHA1FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"
Ft "char *"
Fn SHA1Data "uint8_t *data" "size_t len" "char *buf"
Sh DESCRIPTION
The SHA1 functions implement the NIST Secure Hash Algorithm (SHA-1),
FIPS PUB 180-1.
SHA-1 is used to generate a condensed representation
of a message called a message digest.
The algorithm takes a
message less than 2^64 bits as input and produces a 160-bit digest
suitable for use as a digital signature.
Pp
The SHA1 functions are considered to be more secure than the
Xr md4 3
and
Xr md5 3
functions with which they share a similar interface.
Pp
The
Fn SHA1Init
function initializes a SHA1_CTX
Ar context
for use with
Fn SHA1Update ,
and
Fn SHA1Final .
The
Fn SHA1Update
function adds
Ar data
of length
Ar len
to the SHA1_CTX specified by
Ar context .
Fn SHA1Final
is called when all data has been added via
Fn SHA1Update
and stores a message digest in the
Ar digest
parameter.
When a null pointer is passed to
Fn SHA1Final
as first argument only the final padding will be applied and the
current context can still be used with
Fn SHA1Update .
Pp
The
Fn SHA1Transform
function is used by
Fn SHA1Update
to hash 512-bit blocks and forms the core of the algorithm.
Most programs should use the interface provided by
Fn SHA1Init ,
Fn SHA1Update
and
Fn SHA1Final
instead of calling
Fn SHA1Transform
directly.
Pp
The
Fn SHA1End
function is a front end for
Fn SHA1Final
which converts the digest into an
Tn ASCII
representation of the 160 bit digest in hexadecimal.
Pp
The
Fn SHA1File
function calculates the digest for a file and returns the result via
Fn SHA1End .
If
Fn SHA1File
is unable to open the file a NULL pointer is returned.
Pp
Fn SHA1FileChunk
behaves like
Fn SHA1File
but calculates the digest only for that portion of the file starting at
Fa offset
and continuing for
Fa length
bytes or until end of file is reached, whichever comes first.
A zero
Fa length
can be specified to read until end of file.
A negative
Fa length
or
Fa offset
will be ignored.
Pp
The
Fn SHA1Data
function
calculates the digest of an arbitrary string and returns the result via
Fn SHA1End .
Pp
For each of the
Fn SHA1End ,
Fn SHA1File ,
and
Fn SHA1Data
functions the
Ar buf
parameter should either be a string of at least 41 characters in
size or a NULL pointer.
In the latter case, space will be dynamically
allocated via
Xr malloc 3
and should be freed using
Xr free 3
when it is no longer needed.
Sh EXAMPLES
The follow code fragment will calculate the digest for
the string "abc" which is ``0xa9993e36476816aba3e25717850c26c9cd0d89d''.
Bd -literal -offset indent
SHA1_CTX sha;
uint8_t results[20];
char *buf;
int n;

buf = "abc";
n = strlen(buf);
SHA1Init(&sha);
SHA1Update(&sha, (uint8_t *)buf, n);
SHA1Final(results, &sha);

/* Print the digest as one long hex value */
printf("0x");
for (n = 0; n < 20; n++)
       printf("%02x", results[n]);
putchar('\en');
Ed
Pp
Alternately, the helper functions could be used in the following way:
Bd -literal -offset indent
SHA1_CTX sha;
uint8_t output[41];
char *buf = "abc";

printf("0x%s", SHA1Data(buf, strlen(buf), output));
Ed
Sh SEE ALSO
\"      .Xr sha1 1 ,
Xr md5 1 ,
Xr md4 3 ,
Xr md5 3
Pp
Rs
%A J. Burrows
%T The Secure Hash Standard
%O FIPS PUB 180-1
Re
Sh HISTORY
The SHA-1 functions appeared in
Nx 1.4 .
Sh AUTHORS
This implementation of SHA-1 was written by
An Steve Reid .
Pp
The
Fn SHA1End ,
Fn SHA1File ,
Fn SHA1FileChunk ,
and
Fn SHA1Data
helper functions are derived from code written by Poul-Henning Kamp.
Sh BUGS
This implementation of SHA-1 has not been validated by NIST
and as such is not in official compliance with the standard.
Pp
If a message digest is to be copied to a multi-byte type (ie:
an array of five 32-bit integers) it will be necessary to
perform byte swapping on little endian machines such as the i386, alpha,
and VAX.

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