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

    public static function seal(HiddenString $plaintext, EncryptionPublicKey $publicKey, $encoding = Halite::ENCODE_BASE64URLSAFE) : string
    {
        if (!$publicKey instanceof EncryptionPublicKey) {
            throw new InvalidKey('Argument 2: Expected an instance of EncryptionPublicKey');
        }
        $sealed = \Sodium\crypto_box_seal($plaintext->getString(), $publicKey->getRawKeyMaterial());
        $encoder = Halite::chooseEncoder($encoding);
        if ($encoder) {
            return $encoder($sealed);
        }
        return $sealed;
    }

 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);
     }
 }