Update validatePhpseclib() Method for phpseclib3 Compatibility

[samex]

Hello,

I noticed that the validatePhpseclib() method in /Creativestyle/AmazonCheckout/Model/Debug.php is incompatible with the latest phpseclib3 version installed via Composer.

Current Code (Line 285) :

 public function validatePhpseclib()
    {
        try {
            if (class_exists('Crypt_RSA', false)) {
                $rsa = new Crypt_RSA();
            } elseif (class_exists('\phpseclib\Crypt\RSA', true)) {
                $rsa = new \phpseclib\Crypt\RSA();
            } else {
                return false;
            }

            $rsa->setHash(AmazonPayV2_Client::HASH_ALGORITHM);
            $rsa->setMGFHash(AmazonPayV2_Client::HASH_ALGORITHM);
            $rsa->setSaltLength(20);

            $rsa->loadKey($this->_getDummyPrivateKey());

            if (empty($rsa->modulus) || empty($rsa->exponent)) {
                return false;
            }

        } catch (Exception $e) {
            return false;
        }

        return true;
    }

Issue:

Instantiating the RSA class directly results in a fatal error since the class is abstract in phpseclib3.

Suggested Fix:

    public function validatePhpseclib()
    {
        try {
            if (class_exists('\phpseclib3\Crypt\PublicKeyLoader', true)) {
                $rsa = \phpseclib3\Crypt\PublicKeyLoader::load($this->_getDummyPrivateKey());
            } else {
                return false;
            }
    
            $privateKeyString = $rsa->toString('PKCS1');
            $publicKeyString = $rsa->getPublicKey()->toString('PKCS1');
            if (empty($privateKeyString) || empty($publicKeyString)) {
                return false;
            }
    
        } catch (\Exception $e) {
            return false;
        }
    
        return true;
    }

This update simplifies the validation and ensures compatibility with the newer phpseclib3.

Thank you for considering this change!