src/Gateways/CCAvenueGateway.php
protected function decrypt($encryptedText,$key)
    {
        $secretKey = $this->hextobin(md5($key));
        $initVector = pack("C*", 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f);
        $encryptedText=$this->hextobin($encryptedText);
        $openMode = @mcrypt_module_open(MCRYPT_RIJNDAEL_128, '','cbc', '');
        @mcrypt_generic_init($openMode, $secretKey, $initVector);
        $decryptedText = @mdecrypt_generic($openMode, $encryptedText);
        $decryptedText = rtrim($decryptedText, "\0");
        @mcrypt_generic_deinit($openMode);
        return $decryptedText;

    }
protected function decrypt($encryptedText,$key)
    {
        $secretKey = $this->hextobin(md5($key));
        $initVector = pack("C*", 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f);
        $encryptedText=$this->hextobin($encryptedText);
        $openMode = @mcrypt_module_open(MCRYPT_RIJNDAEL_128, '','cbc', '');
        @mcrypt_generic_init($openMode, $secretKey, $initVector);
        $decryptedText = @mdecrypt_generic($openMode, $encryptedText);
        $decryptedText = rtrim($decryptedText, "\0");
        @mcrypt_generic_deinit($openMode);
        return $decryptedText;

    }
CCAvenue Decrypt Function

@param $encryptedText
@param $key
@return string