I'm trying to write a script to encrypt a string that can be decrypted using the method descried here. While the script does get a value that at first glance looks correct it does not decrypt correctly. The output can be tested here. 
#!/usr/bin/perl -w
use strict;
use Digest::HMAC_SHA1 qw(hmac_sha1);
use MIME::Base64::URLSafe;
use MIME::Base64;

my $initvectorsize = 16;
my $ciphertextsize = 8;
my $signaturesize = 4;
my $encryptedvaluesize = $initvectorsize + $ciphertextsize + $signatur
+esize;

my $encryptionkey = 'c488fdd0d81f';
my $integritykey = 'fe3fd7cc8731';
my $plaintext = '';
my $digest = '';
my $initvector = '';
my $ciphertext = '';
my $signature = '';
my $output = '';

print "Enter price to encrypt:";
chomp (my $input = <>);
$plaintext = $input;

for (my$c=0;$c<$initvectorsize;$c++) {
    $initvector = $initvector.int(rand(10));
}

$digest = hmac_sha1($initvector, $encryptionkey);
$ciphertext = $digest ^ $plaintext;

$signature = hmac_sha1($plaintext.$initvector, $integritykey);

$output = $initvector.substr($ciphertext, 0, $ciphertextsize).substr($
+signature, 0, $signaturesize);

print "ERROR: Bad encrypted length!\n" if (length($output) != $encrypt
+edvaluesize);

$output = urlsafe_b64encode($output);

print "ERROR: Bad base64 encoded length!\n" if (length($output) != 38)
+;
print "Encrypted Price:'$output'\n";

[download]
Any thoughts or advice?

In reply to Private Data Communication Protocol Encryption by pishposh30

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