ParagonIE\Halite\Asymmetric\Crypto::unseal PHP Method

    public static function unseal(string $ciphertext, EncryptionSecretKey $privateKey, $encoding = Halite::ENCODE_BASE64URLSAFE) : HiddenString
    {
        $decoder = Halite::chooseEncoder($encoding, true);
        if ($decoder) {
            // We were given hex data:
            try {
                $ciphertext = $decoder($ciphertext);
            } catch (\RangeException $ex) {
                throw new InvalidMessage('Invalid character encoding');
            }
        }
        // Get a box keypair (needed by crypto_box_seal_open)
        $secret_key = $privateKey->getRawKeyMaterial();
        $public_key = \Sodium\crypto_box_publickey_from_secretkey($secret_key);
        $key_pair = \Sodium\crypto_box_keypair_from_secretkey_and_publickey($secret_key, $public_key);
        // Wipe these immediately:
        \Sodium\memzero($secret_key);
        \Sodium\memzero($public_key);
        // Now let's open that sealed box
        $message = \Sodium\crypto_box_seal_open($ciphertext, $key_pair);
        // Always memzero after retrieving a value
        \Sodium\memzero($key_pair);
        if ($message === false) {
            throw new InvalidKey('Incorrect secret key for this sealed message');
        }
        // We have our encrypted message here
        return new HiddenString($message);
    }

 public function testSealFail()
 {
     $alice = KeyPair::generate();
     $message = 'This is for your eyes only';
     $sealed = Asymmetric::seal($message, $alice->getPublicKey(), true);
     // Let's flip one bit, randomly:
     $r = \Sodium\randombytes_uniform(\mb_strlen($sealed, '8bit'));
     $amt = 1 << \Sodium\randombytes_uniform(8);
     $sealed[$r] = \chr(\ord($sealed[$r]) ^ $amt);
     // This should throw an exception
     try {
         $opened = Asymmetric::unseal($sealed, $alice->getSecretKey(), true);
         $this->assertEquals($opened, $message);
         throw new Exception('ERROR: THIS SHOULD ALWAYS FAIL');
     } catch (CryptoException\InvalidKey $e) {
         $this->assertTrue($e instanceof CryptoException\InvalidKey);
     } catch (CryptoException\InvalidMessage $e) {
         $this->assertTrue($e instanceof CryptoException\InvalidMessage);
     }
 }