.\" $NetBSD: sha3.3,v 1.1 2017/11/30 16:00:48 wiz Exp $
.\"
.\" Copyright (c) 2015 Taylor R. Campbell
.\" All rights reserved.
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.Dd October 14, 2015
.Dt SHA3 3
.Os
.Sh NAME
.Nm SHA3
.Nd NIST FIPS PUB 202: SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions
.Sh SYNOPSIS
.In sha3.h
.Ft void
.Fn SHA3_224_Init "SHA3_224_CTX *ctx"
.Ft void
.Fn SHA3_224_Update "SHA3_224_CTX *ctx" "const uint8_t *buf" "size_t len"
.Ft void
.Fn SHA3_224_Final "uint8_t digest[SHA3_224_DIGEST_LENGTH]" "SHA3_224_CTX *ctx"
.Ft void
.Fn SHA3_256_Init "SHA3_256_CTX *ctx"
.Ft void
.Fn SHA3_256_Update "SHA3_256_CTX *ctx" "const uint8_t *buf" "size_t len"
.Ft void
.Fn SHA3_256_Final "uint8_t digest[SHA3_256_DIGEST_LENGTH]" "SHA3_256_CTX *ctx"
.Ft void
.Fn SHA3_384_Init "SHA3_384_CTX *ctx"
.Ft void
.Fn SHA3_384_Update "SHA3_384_CTX *ctx" "const uint8_t *buf" "size_t len"
.Ft void
.Fn SHA3_384_Final "uint8_t digest[SHA3_384_DIGEST_LENGTH]" "SHA3_384_CTX *ctx"
.Ft void
.Fn SHA3_512_Init "SHA3_512_CTX *ctx"
.Ft void
.Fn SHA3_512_Update "SHA3_512_CTX *ctx" "const uint8_t *buf" "size_t len"
.Ft void
.Fn SHA3_512_Final "uint8_t digest[SHA3_512_DIGEST_LENGTH]" "SHA3_512_CTX *ctx"
.Sh DESCRIPTION
The
.Nm
functions implement the cryptographic hash functions of the NIST SHA-3
standard, FIPS PUB 202.
The
.Nm
functions compress an arbitrary-length message m into short
fixed-length octet strings SHA3-224(m), SHA3-256(m), etc., called a
cryptographic digest or hash.
.Pp
Before using the
.Nm
functions, applications should first call
.Xr SHA3_Selftest 3
and confirm that it succeeded.
.Pp
Only the
.Nm SHA3_256
functions are specified in detail; the
.Nm SHA3_224 ,
.Nm SHA3_384 ,
and
.Nm SHA3_512
functions are exactly analogous.
.Pp
The caller must allocate memory for a
.Vt SHA3_256_CTX
object to hold the state of a SHA3-256 hash computation over a
message.
.Vt SHA3_256_CTX
objects are slightly over 200 bytes, and may be copied or relocated in
memory.
.Bl -tag -width abcd
.It Fn SHA3_256_Init "ctx"
Initialize a SHA3-256 context.
Must be done before any other operations on
.Fa ctx .
.It Fn SHA3_256_Update "ctx" "data" "len"
Append
.Fa len
octets at
.Fa data
to the message.
.It Fn SHA3_256_Final "digest" "ctx"
Store at
.Fa digest
the 32-octet SHA3-256 hash of the message obtained by concatenating
all prior inputs to
.Fn SHA3_256_Update
on
.Fa ctx .
.Pp
Subsequent use of
.Fa ctx
is not allowed, unless it is reinitialized with
.Fn SHA3_256_Init .
.El
.Sh SEE ALSO
.Xr keccak 3 ,
.Xr SHA3_Selftest 3 ,
.Xr SHAKE 3
.Sh STANDARDS
.Rs
.%A National Institute of Standards and Technology
.%T SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions
.%O FIPS PUB 202
.%D August 2015
.Re
.Sh AUTHORS
.An Taylor R Campbell Aq campbell+sha3@mumble.net