GMS-2016-16: AES-GCM nonce reuse vulnerability

The package encryptor encrypts all messages using the same key/nonce. This not only exposes the XOR of the plaintexts if you XOR together two ciphertexts, but it also leaks the AES-GCM authentication key, allowing an attacker to forge messages and potentially perform chosen ciphertext attacks, which could potentially enable full plaintext recovery.