HMAC en perl

Bonjour =E0 tous,

J'ai fait une impl=E9mentation rapide de l'algo HMAC en perl. Une petite
relecture serait la bienvenue, si certains d'entre vous ont 2 minutes
=E0 y consacrer.....

Merci,
Julien

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#! /usr/bin/perl -w

use strict;

##################################
## impl=E9mentation HMAC RFC 2104 ##
## j. vehent - mai 2008 ##
##################################

use Digest::SHA1 qw(sha1);
use MIME::Base64;

my ($K, $text, $H); # 'K' the key, 'text' the data to compute the hmac
on, 'H' the HMAC
my $B =3D 64; # block size in bytes
print "\ninput HMAC key in base 64 form -> ";
$K =3D decode_base64(<STDIN>);

print "\ninput ASCII data to compute HMAC on -> ";
$text =3D <STDIN>;

# if key length > block size, reset key to sha1(key)
$K =3D sha1($K) if length($K) > $B;

# ipad =3D key xor '0x36' b times
my $k_ipad =3D $K ^ (chr(0x36) x $B);

# opad =3D key xor '0x5c' b times
my $k_opad =3D $K ^ (chr(0x5c) x $B);


# HMAC =3D sha1((key xor '0x5c'*B) || sha1((key xor '0x36'*B) || text))
# with || is concatenation

$H =3D sha1($k_ipad.$text);

$H =3D sha1($k_opad.$H);

print "\n\nHMAC =3D ".unpack("H*", $H)."\n\n";