// decrypt the request
        try
        {
                string cipher;
                string stemp((char*)request, strlen((char*)request));
                StringSource source(stemp.data(), true, new Base64Decoder(new
StringSink(cipher)));

                SecByteBlock key((const byte*)&keydat[0], 32);

                EAX< AES >::Decryption d;
                d.SetKeyWithIV( key, key.size(), (const byte*)cipher.data(), 12 );
                cipher.erase(0, 12);

                // Break the cipher text out into it's components: Encrypted Data
and MAC Value
                string enc = cipher.substr( 0, cipher.length()-TAG_SIZE );
                string mac = cipher.substr( cipher.length()-TAG_SIZE );

                // Sanity checks
                assert( cipher.size() == enc.size() + mac.size() );
                assert( TAG_SIZE == mac.size() );

                AuthenticatedDecryptionFilter df( d, NULL,
AuthenticatedDecryptionFilter::MAC_AT_BEGIN |
AuthenticatedDecryptionFilter::THROW_EXCEPTION, TAG_SIZE );

                // The order of the following calls are important
                df.ChannelPut( "", (const byte*)mac.data(), mac.size() );
                df.ChannelPut( "AAD", (const byte*)(char*)licenseID,
strlen((char*)licenseID));
                df.ChannelPut( "", (const byte*)enc.data(), enc.size() );

                // If the object throws, it will most likely occur during ChannelMessageEnd()
                df.ChannelMessageEnd( "AAD" );
                df.ChannelMessageEnd( "" );

                // If the object does not throw, here's the only opportunity to
check the data's integrity
                bool b = df.GetLastResult();
                assert( b );

                // Remove data from channel
                size_t n = (size_t)-1;

                // Plain text recovered from enc.data()
                df.SetRetrievalChannel( "" );
                n = (size_t)df.MaxRetrievable();
                retrieved.resize( n );

                if( n > 0 ) { df.Get( (byte*)retrieved.data(), n ); }
        }
        catch( CryptoPP::InvalidArgument& e )
        {
                hr = E_PGNPDECRYPTFAIL;
        }
        catch( CryptoPP::AuthenticatedSymmetricCipher::BadState& e )
        {
                // Pushing PDATA before ADATA results in: "GMC/AES: Update was
called before State_IVSet"
                hr = E_PGNPDECRYPTFAIL;
        }
        catch( CryptoPP::HashVerificationFilter::HashVerificationFailed& e )
        {
                hr = E_PGNPDECRYPTFAIL;
        }

<?php
$request = "XP/4lQ3gMwQyuNDwxo3gFn9NmsUlfqhr6aTLprg0FJ6a7utrnbzUnT/8fPI7b0bldbom94eK".
"FZsVzlGcPnqbMCuKSTrQGt9b60ZBciMtGO2hVioIp1Vb2U+t16UHqwXwFlPddC5DCNiiTg5W".
"XBugH3POuWypZvbd4";

$source = base64_decode($request);

$cipher = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, '');

$iv_size = mcrypt_enc_get_iv_size($cipher);
printf("iv_size = %d\n",$iv_size);
...
?>