libc/hash/hmac.3

hmac.3 revision 1.2  $NetBSD: hmac.3,v 1.2 2016/07/01 22:56:06 christos Exp $

.Dd July 1, 2016
.Dt HMAC 3
.Os
.Sh NAME
.Nm hmac ,
.Nd Compute a key-Hash Message Authentication Code
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
n stdlib.h .Ft ssize_t
.Fn hmac "const char *hname" "const void *key" "size_t klen" "const void *text" "size_t tlen" "void *digest" "size_t dlen"
.Sh DESCRIPTION
The
.Fn hmac
function computes the key-Hash Message Authentication Code per
.%R RFC 2104
and places the result in
.Fa digest
writing up to
.Fa dlen
bytes.
The actual number of bytes that would be written is returned.
p
The hash functions supported are: md2, md4, md5, rmd160, sha1, sha224,
sha256, sha384, sha512.
.Sh RETURN VALUES
The
.Fn hmac
returns
.Dv -1
if the
.Fa hname
is not found.
Otherwise the actual length of the digest string is returned (which could
be bigger or smaller than
.Fa dlen ) .
This length depends on the hashing function selected.
.Sh SEE ALSO
.Xr md2 3 ,
.Xr md4 3 ,
.Xr md5 3 ,
.Xr rmd160 3 ,
.Xr sha1 3 ,
.Xr sha2 3
.Sh STANDARDS
.%R RFC 2104
.Sh NOTES
The maximum digest length has been extended from
.Dv 64
to
.Dv 128
bytes to handle SHA2.
.Sh HISTORY
The
.Fn hmac
function appeared in
.Nx 8