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package Digest::HMAC;
$VERSION = "1.03";
use strict;
# OO interface
sub new
{
my($class, $key, $hasher, $block_size) = @_;
$block_size ||= 64;
$key = $hasher->new->add($key)->digest if length($key) > $block_size;
my $self = bless {}, $class;
$self->{k_ipad} = $key ^ (chr(0x36) x $block_size);
$self->{k_opad} = $key ^ (chr(0x5c) x $block_size);
$self->{hasher} = $hasher->new->add($self->{k_ipad});
$self;
}
sub reset
{
my $self = shift;
$self->{hasher}->reset->add($self->{k_ipad});
$self;
}
sub add { my $self = shift; $self->{hasher}->add(@_); $self; }
sub addfile { my $self = shift; $self->{hasher}->addfile(@_); $self; }
sub _digest
{
my $self = shift;
my $inner_digest = $self->{hasher}->digest;
$self->{hasher}->reset->add($self->{k_opad}, $inner_digest);
}
sub digest { shift->_digest->digest; }
sub hexdigest { shift->_digest->hexdigest; }
sub b64digest { shift->_digest->b64digest; }
# Functional interface
require Exporter;
*import = \&Exporter::import;
use vars qw(@EXPORT_OK);
@EXPORT_OK = qw(hmac hmac_hex);
sub hmac
{
my($data, $key, $hash_func, $block_size) = @_;
$block_size ||= 64;
$key = &$hash_func($key) if length($key) > $block_size;
my $k_ipad = $key ^ (chr(0x36) x $block_size);
my $k_opad = $key ^ (chr(0x5c) x $block_size);
&$hash_func($k_opad, &$hash_func($k_ipad, $data));
}
sub hmac_hex { unpack("H*", &hmac); }
1;
__END__
=head1 NAME
Digest::HMAC - Keyed-Hashing for Message Authentication
=head1 SYNOPSIS
# Functional style
use Digest::HMAC qw(hmac hmac_hex);
$digest = hmac($data, $key, \&myhash);
print hmac_hex($data, $key, \&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;
=head1 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 C<Digest::> interface, but the constructor
takes the secret key and the name of some other simple C<Digest::>
as argument.
The hmac() and hmac_hex() functions and the Digest::HMAC->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.
=head1 SEE ALSO
L<Digest::HMAC_MD5>, L<Digest::HMAC_SHA1>
RFC 2104
=head1 AUTHORS
Graham Barr <gbarr@ti.com>, Gisle Aas <gisle@aas.no>
=cut
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