\" $NetBSD: sha2.3,v 1.9 2018/10/09 11:36:35 kamil Exp $
\"      $OpenBSD: sha2.3,v 1.11 2004/06/22 01:57:29 jfb Exp $
\"
\" Copyright (c) 2003, 2004 Todd C. Miller <[email protected]>
\"
\" 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.
\"
\" Sponsored in part by the Defense Advanced Research Projects
\" Agency (DARPA) and Air Force Research Laboratory, Air Force
\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
\"
\" See http://www.nist.gov/sha/ for the detailed standard
\"
Dd October 9, 2018
Dt SHA2 3
Os
Sh NAME
Nm SHA224_Init ,
Nm SHA224_Update ,
Nm SHA224_Final ,
Nm SHA224_Transform ,
Nm SHA224_End ,
Nm SHA224_File ,
Nm SHA224_FileChunk ,
Nm SHA224_Data ,
Nm SHA256_Init ,
Nm SHA256_Update ,
Nm SHA256_Final ,
Nm SHA256_Transform ,
Nm SHA256_End ,
Nm SHA256_File ,
Nm SHA256_FileChunk ,
Nm SHA256_Data ,
Nm SHA384_Init ,
Nm SHA384_Update ,
Nm SHA384_Final ,
Nm SHA384_Transform ,
Nm SHA384_End ,
Nm SHA384_File ,
Nm SHA384_FileChunk ,
Nm SHA384_Data ,
Nm SHA512_Init ,
Nm SHA512_Update ,
Nm SHA512_Final ,
Nm SHA512_Transform ,
Nm SHA512_End ,
Nm SHA512_File ,
Nm SHA512_FileChunk ,
Nm SHA512_Data
Nd calculate the NIST Secure Hash Standard (version 2)
Sh SYNOPSIS
In sys/types.h
In sha2.h
Ft void
Fn SHA224_Init "SHA224_CTX *context"
Ft void
Fn SHA224_Update "SHA224_CTX *context" "const uint8_t *data" "size_t len"
Ft void
Fn SHA224_Final "uint8_t digest[SHA224_DIGEST_LENGTH]" "SHA224_CTX *context"
Ft void
Fn SHA224_Transform "uint32_t state[8]" "const uint8_t buffer[SHA224_BLOCK_LENGTH]"
Ft "char *"
Fn SHA224_End "SHA224_CTX *context" "char *buf"
Ft "char *"
Fn SHA224_File "const char *filename" "char *buf"
Ft "char *"
Fn SHA224_FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"
Ft "char *"
Fn SHA224_Data "uint8_t *data" "size_t len" "char *buf"
Ft void
Fn SHA256_Init "SHA256_CTX *context"
Ft void
Fn SHA256_Update "SHA256_CTX *context" "const uint8_t *data" "size_t len"
Ft void
Fn SHA256_Final "uint8_t digest[SHA256_DIGEST_LENGTH]" "SHA256_CTX *context"
Ft void
Fn SHA256_Transform "uint32_t state[8]" "const uint8_t buffer[SHA256_BLOCK_LENGTH]"
Ft "char *"
Fn SHA256_End "SHA256_CTX *context" "char *buf"
Ft "char *"
Fn SHA256_File "const char *filename" "char *buf"
Ft "char *"
Fn SHA256_FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"
Ft "char *"
Fn SHA256_Data "uint8_t *data" "size_t len" "char *buf"
Ft void
Fn SHA384_Init "SHA384_CTX *context"
Ft void
Fn SHA384_Update "SHA384_CTX *context" "const uint8_t *data" "size_t len"
Ft void
Fn SHA384_Final "uint8_t digest[SHA384_DIGEST_LENGTH]" "SHA384_CTX *context"
Ft void
Fn SHA384_Transform "uint64_t state[8]" "const uint8_t buffer[SHA384_BLOCK_LENGTH]"
Ft "char *"
Fn SHA384_End "SHA384_CTX *context" "char *buf"
Ft "char *"
Fn SHA384_File "char *filename" "char *buf"
Ft "char *"
Fn SHA384_FileChunk "char *filename" "char *buf" "off_t offset" "off_t length"
Ft "char *"
Fn SHA384_Data "uint8_t *data" "size_t len" "char *buf"
Ft void
Fn SHA512_Init "SHA512_CTX *context"
Ft void
Fn SHA512_Update "SHA512_CTX *context" "const uint8_t *data" "size_t len"
Ft void
Fn SHA512_Final "uint8_t digest[SHA512_DIGEST_LENGTH]" "SHA512_CTX *context"
Ft void
Fn SHA512_Transform "uint64_t state[8]" "const uint8_t buffer[SHA512_BLOCK_LENGTH]"
Ft "char *"
Fn SHA512_End "SHA512_CTX *context" "char *buf"
Ft "char *"
Fn SHA512_File "char *filename" "char *buf"
Ft "char *"
Fn SHA512_FileChunk "char *filename" "char *buf" "off_t offset" "off_t length"
Ft "char *"
Fn SHA512_Data "uint8_t *data" "size_t len" "char *buf"
Sh DESCRIPTION
The SHA2 functions implement the NIST Secure Hash Standard,
FIPS PUB 180-2.
The SHA2 functions are used to generate a condensed representation of a
message called a message digest, suitable for use as a digital signature.
There are four families of functions, with names corresponding to
the number of bits in the resulting message digest.
The SHA-224 and SHA-256 functions are limited to processing a message of less
than 2^64 bits as input.
The SHA-384 and SHA-512 functions can process a message of at most 2^128 - 1
bits as input.
Pp
The SHA2 functions are considered to be more secure than the
Xr sha1 3
functions with which they share a similar interface.
The 224, 256, 384, and 512-bit versions of SHA2 share the same interface.
For brevity, only the 256-bit variants are described below.
Pp
The
Fn SHA256_Init
function initializes a SHA256_CTX
Ar context
for use with
Fn SHA256_Update ,
and
Fn SHA256_Final .
The
Fn SHA256_Update
function adds
Ar data
of length
Ar len
to the SHA256_CTX specified by
Ar context .
Fn SHA256_Final
is called when all data has been added via
Fn SHA256_Update
and stores a message digest in the
Ar digest
parameter.
Pp
The
Fn SHA256_Transform
function is used by
Fn SHA256_Update
to hash 512-bit blocks and forms the core of the algorithm.
Most programs should use the interface provided by
Fn SHA256_Init ,
Fn SHA256_Update ,
and
Fn SHA256_Final
instead of calling
Fn SHA256_Transform
directly.
Pp
The
Fn SHA256_End
function is a front end for
Fn SHA256_Final
which converts the digest into an ASCII representation of the digest
in hexadecimal.
Pp
The
Fn SHA256_File
function calculates the digest for a file and returns the result via
Fn SHA256_End .
If
Fn SHA256_File
is unable to open the file, a
Dv NULL
pointer is returned.
Pp
Fn SHA256_FileChunk
behaves like
Fn SHA256_File
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 SHA256_Data
function
calculates the digest of an arbitrary string and returns the result via
Fn SHA256_End .
Pp
For each of the
Fn SHA256_End ,
Fn SHA256_File ,
Fn SHA256_FileChunk ,
and
Fn SHA256_Data
functions the
Ar buf
parameter should either be a string large enough to hold the resulting digest
(e.g.,
Ev SHA224_DIGEST_STRING_LENGTH ,
Ev SHA256_DIGEST_STRING_LENGTH ,
Ev SHA384_DIGEST_STRING_LENGTH ,
or
Ev SHA512_DIGEST_STRING_LENGTH ,
depending on the function being used)
or a
Dv 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 following code fragment will calculate the SHA-256 digest for the string
Qq abc ,
which is
Dq 0xba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad .
Bd -literal -offset indent
SHA256_CTX ctx;
uint8_t results[SHA256_DIGEST_LENGTH];
char *buf;
int n;

buf = "abc";
n = strlen(buf);
SHA256_Init(&ctx);
SHA256_Update(&ctx, (uint8_t *)buf, n);
SHA256_Final(results, &ctx);

/* Print the digest as one long hex value */
printf("0x");
for (n = 0; n < SHA256_DIGEST_LENGTH; n++)
       printf("%02x", results[n]);
putchar('\en');
Ed
Pp
Alternately, the helper functions could be used in the following way:
Bd -literal -offset indent
SHA256_CTX ctx;
uint8_t output[SHA256_DIGEST_STRING_LENGTH];
char *buf = "abc";

printf("0x%s\en", SHA256_Data(buf, strlen(buf), output));
Ed
Sh SEE ALSO
Xr cksum 1 ,
Xr md4 3 ,
Xr md5 3 ,
Xr rmd160 3 ,
Xr sha1 3
Rs
%T Secure Hash Standard
%O FIPS PUB 180-2
Re
Sh HISTORY
The SHA2 functions appeared in
Ox 3.4
and
Nx 3.0 .
Sh AUTHORS
An -nosplit
This implementation of the SHA functions was written by
An Aaron D. Gifford .
Pp
The
Fn SHA256_End ,
Fn SHA256_File ,
Fn SHA256_FileChunk ,
and
Fn SHA256_Data
helper functions are derived from code written by
An Poul-Henning Kamp .
Sh CAVEATS
This implementation of the Secure Hash Standard 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 (i.e.:
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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