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.\" ========================================================================
.\"
.IX Title "Digest::HMAC 3"
.TH Digest::HMAC 3 "2021-04-01" "perl v5.26.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Digest::HMAC \- Keyed\-Hashing for Message Authentication
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 4
\& # Functional style
\& use Digest::HMAC qw(hmac hmac_hex);
\& $digest = hmac($data, $key, \e&myhash);
\& print hmac_hex($data, $key, \e&myhash);
\&
\& # OO style
\& use Digest::HMAC;
\& $hmac = Digest::HMAC\->new($key, "Digest::MyHash");
\&
\& $hmac\->add($data);
\& $hmac\->addfile(*FILE);
\&
\& $digest = $hmac\->digest;
\& $digest = $hmac\->hexdigest;
\& $digest = $hmac\->b64digest;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\s-1HMAC\s0 is used for message integrity checks between two parties that
share a secret key, and works in combination with some other Digest
algorithm, usually \s-1MD5\s0 or \s-1SHA\-1.\s0  The \s-1HMAC\s0 mechanism is described in
\&\s-1RFC 2104.\s0
.PP
\&\s-1HMAC\s0 follow the common \f(CW\*(C`Digest::\*(C'\fR interface, but the constructor
takes the secret key and the name of some other simple \f(CW\*(C`Digest::\*(C'\fR
as argument.
.PP
The \fBhmac()\fR and \fBhmac_hex()\fR functions and the Digest::HMAC\->\fBnew()\fR constructor
takes an optional \f(CW$blocksize\fR argument as well.  The \s-1HMAC\s0 algorithm assumes the
digester to hash by iterating a basic compression function on blocks of data
and the \f(CW$blocksize\fR should match the byte-length of such blocks.
.PP
The default \f(CW$blocksize\fR is 64 which is suitable for the \s-1MD5\s0 and \s-1SHA\-1\s0 digest
functions.  For stronger algorithms the blocksize probably needs to be
increased.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Digest::HMAC_MD5, Digest::HMAC_SHA1
.PP
\&\s-1RFC 2104\s0
.SH "MAINTAINER"
.IX Header "MAINTAINER"
Andrew Rodland <arodland@cpan.org>
.SH "ORIGINAL AUTHORS"
.IX Header "ORIGINAL AUTHORS"
Graham Barr <gbarr@ti.com>, Gisle Aas <gisle@aas.no>