private static void validate(AesCtrHmacAeadParameters parameters)
      throws GeneralSecurityException {
    if (parameters.getAesKeySizeBytes() != 16 && parameters.getAesKeySizeBytes() != 32) {
      throw new GeneralSecurityException("AES key size must be 16 or 32 bytes");
    }
  }
This key manager generates new {@link AesCtrHmacAeadKey} keys and produces new instances of
{@link EncryptThenAuthenticate}.
java_src/src/main/java/com/google/crypto/tink/aead/AesCtrHmacAeadKeyManager.java