private byte[] noPrefixEncrypt(final byte[] plaintext, final byte[] contextInfo)
      throws GeneralSecurityException {
    byte[] info = contextInfo;
    if (info == null) {
      info = new byte[0];
    }
    HpkeContext context = HpkeContext.createSenderContext(recipientPublicKey, kem, kdf, aead, info);
    byte[] ciphertext = context.seal(plaintext, EMPTY_ASSOCIATED_DATA);
    return com.google.crypto.tink.subtle.Bytes.concat(context.getEncapsulatedKey(), ciphertext);
  }
Hybrid Public Key Encryption (HPKE) encryption.

<p>HPKE RFC: https://www.rfc-editor.org/rfc/rfc9180.html
java_src/src/main/java/com/google/crypto/tink/hybrid/internal/HpkeEncrypt.java