@AccessesPartialKey
  public static Aead create(XChaCha20Poly1305Key key) throws GeneralSecurityException {
    return new XChaCha20Poly1305Jce(
        key.getKeyBytes().toByteArray(InsecureSecretKeyAccess.get()),
        key.getOutputPrefix().toByteArray());
  }
ChaCha20Poly1305Jce implements an AEAD for ChaCha20Poly1305, as described in <a
href="https://tools.ietf.org/html/rfc8439#section-2.8">RFC 8439, section 2.8</a>.

<p>It uses the JCE, and requires that algorithm "ChaCha20-Poly1305" is present.
java_src/src/main/java/com/google/crypto/tink/aead/internal/XChaCha20Poly1305Jce.java