@Override
  public boolean equalsKey(Key o) {
    if (!(o instanceof ChaCha20Poly1305Key)) {
      return false;
    }
    ChaCha20Poly1305Key that = (ChaCha20Poly1305Key) o;
    // Since outputPrefix is a function of parameters, we can ignore it here.
    return that.parameters.equals(parameters)
        && that.keyBytes.equalsSecretBytes(keyBytes)
        && Objects.equals(that.idRequirement, idRequirement);
  }
Represents the Aead ChaCha20-Poly1305 specified in RFC 8439.

<p>ChaCha20-Poly1305 allows no parameters; hence the main part here is really just the keys.
However, Tink allows prefixing every ciphertext with an ID-dependent prefix, see {@link
ChaCha20Poly1305Parameters.Variant}.
java_src/src/main/java/com/google/crypto/tink/aead/ChaCha20Poly1305Key.java