@Override
  public byte[] encrypt(final byte[] plaintext, final byte[] contextInfo)
      throws GeneralSecurityException {
    if (outputPrefix.length == 0) {
      return rawHybridEncrypt.encrypt(plaintext, contextInfo);
    }
    return Bytes.concat(outputPrefix, rawHybridEncrypt.encrypt(plaintext, contextInfo));
  }
This method covers the cases where users created their own aead/key classes.
java_src/src/main/java/com/google/crypto/tink/hybrid/internal/LegacyFullHybridEncrypt.java