# phpman > man > Digest::HMAC(3pm)

## NAME
    [Digest::HMAC](https://www.chedong.com/phpMan.php/perldoc/Digest%3A%3AHMAC/markdown) - Keyed-Hashing for Message Authentication

## SYNOPSIS
     # Functional style
     use [Digest::HMAC](https://www.chedong.com/phpMan.php/perldoc/Digest%3A%3AHMAC/markdown) qw(hmac hmac_hex);
     $digest = hmac($data, $key, \&myhash);
     print hmac_hex($data, $key, \&myhash);

     # OO style
     use [Digest::HMAC](https://www.chedong.com/phpMan.php/perldoc/Digest%3A%3AHMAC/markdown);
     $hmac = [Digest::HMAC](https://www.chedong.com/phpMan.php/perldoc/Digest%3A%3AHMAC/markdown)->new($key, "[Digest::MyHash](https://www.chedong.com/phpMan.php/perldoc/Digest%3A%3AMyHash/markdown)");

     $hmac->add($data);
     $hmac->addfile(*FILE);

     $digest = $hmac->digest;
     $digest = $hmac->hexdigest;
     $digest = $hmac->b64digest;

## DESCRIPTION
    HMAC is used for message integrity checks between two parties that share a secret key, and works
    in combination with some other Digest algorithm, usually MD5 or SHA-1. The HMAC mechanism is
    described in RFC 2104.

    HMAC follow the common "Digest::" interface, but the constructor takes the secret key and the
    name of some other simple "Digest::" as argument.

    The hmac() and hmac_hex() functions and the [Digest::HMAC](https://www.chedong.com/phpMan.php/perldoc/Digest%3A%3AHMAC/markdown)->new() constructor takes an optional
    $blocksize argument as well. The HMAC algorithm assumes the digester to hash by iterating a
    basic compression function on blocks of data and the $blocksize should match the byte-length of
    such blocks.

    The default $blocksize is 64 which is suitable for the MD5 and SHA-1 digest functions. For
    stronger algorithms the blocksize probably needs to be increased.

## SEE ALSO
    [Digest::HMAC_MD5](https://www.chedong.com/phpMan.php/perldoc/Digest%3A%3AHMACMD5/markdown), [Digest::HMAC_SHA1](https://www.chedong.com/phpMan.php/perldoc/Digest%3A%3AHMACSHA1/markdown)

    RFC 2104

## MAINTAINER
    Andrew Rodland <<arodland@cpan.org>>

## ORIGINAL AUTHORS
    Graham Barr <<gbarr@ti.com>>, Gisle Aas <<gisle@aas.no>>