\" $NetBSD: hmac.3,v 1.6 2018/05/23 02:08:40 christos Exp $
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\" by Christos Zoulas.
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Dd May 22, 2018
Dt HMAC 3
Os
Sh NAME
Nm hmac
Nd compute a key-Hash Message Authentication Code
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In 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
Tn 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.
Pp
The hash functions supported are: md2, md4, md5, rmd160, sha1, sha224,
sha256, sha384, and sha512.
Sh RETURN VALUES
The
Fn hmac
function 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 openssl_HMAC 3 ,
Xr openssl_MD2 3 ,
Xr openssl_MD4 3 ,
Xr openssl_MD5 3 ,
Xr rmd160 3 ,
Xr sha1 3 ,
Xr sha2 3
Sh STANDARDS
Rs
%R RFC 2104
Re
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 .
