cryb-to/lib/digest/cryb_sha256.3

.\"-
.\" Copyright (c) 2015 Universitetet i Oslo
.\" Copyright (c) 2016 Dag-Erling Smørgrav
.\" 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. The name of the author may not be used to endorse or promote
.\"    products derived from this software without specific prior written
.\"    permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS 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 AUTHOR OR 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 September 17, 2016
.Dt CRYB_SHA256 3
.Os
.Sh NAME
.Nm cryb_sha256_init ,
.Nm cryb_sha256_update ,
.Nm cryb_sha256_final ,
.Nm cryb_sha256_complete
.Nd Secure Hash Algorithm 2
.Sh LIBRARY
.Lb libcryb-digest
.Sh SYNOPSIS
.In stddef.h
.In stdint.h
.In cryb/sha256.h
.Ft void
.Fn cryb_sha256_init "cryb_sha256_ctx *context"
.Ft void
.Fn cryb_sha256_update "cryb_sha256_ctx *context" "const void *data" "size_t len"
.Ft void
.Fn cryb_sha256_final "cryb_sha256_ctx *context" "uint8_t *digest"
.Ft void
.Fn cryb_sha256_complete "const void *data" "size_t len" "uint8_t *digest"
.Sh DESCRIPTION
The
.Nm cryb_sha256
family of functions implements the NIST SHA-256 message digest
algorithm as described in FIPS 180-4.
.Pp
The
.Fn cryb_sha256_init
function initializes the context structure pointed to by
.Va context .
It is the caller's responsibility to allocate this structure.
.Pp
The
.Fn cryb_sha256_update
function hashes the next
.Va len
bytes of data pointed to by the
.Va data
pointer into the given hash context.
.Pp
The
.Fn cryb_sha256_final
function finalizes the computation and writes the resulting message
digest to the caller-provided buffer pointed to by
.Va digest ,
which must be at least
.Dv SHA256_DIGEST_LEN
bytes long.
It is the caller's responsibility to dispose of the context structure
after calling
.Fn cryb_sha256_final .
.Pp
The
.Fn cryb_sha256_complete
function is a shortcut to calling
.Fn cryb_sha256_init ,
.Fn cryb_sha256_update
and
.Fn cryb_sha256_final
when the entire message is available up front in a single contiguous
buffer.
.Sh IMPLEMENTATION NOTES
The
.In cryb/sha256.h
header provides macros which allows these functions and the context
type to be referred to without their
.Dq Li cryb_
prefix.
.Sh SEE ALSO
.Xr cryb_digest 3 ,
.Xr cryb_sha1 3 ,
.Xr cryb_sha224 3 ,
.Xr cryb_sha384 3 ,
.Xr cryb_sha512 3
.Sh REFERENCES
.Rs
.%Q National Institute of Standards and Technology
.%R Secure Hash Standard (SHS) (FIPS PUB 180-4)
.%D March 2012
.Re
.Sh AUTHORS
These functions and this manual page were written for the University
of Oslo by
.An Dag-Erling Sm\(/orgrav Aq Mt d.e.smorgrav@usit.uio.no .