code: @Restricted(NoExternalUse.class) // TODO pending API
      public Cipher encrypt(byte[] iv) {
          try {
              Cipher cipher = Secret.getCipher(ALGORITHM);
              cipher.init(Cipher.ENCRYPT_MODE, getKey(), new IvParameterSpec(iv));
              return cipher;
          } catch (GeneralSecurityException e) {
              throw new AssertionError(e);
          }
      }
docs: Returns a {@link Cipher} object for encrypting with this key using the provided initialization vector.
  @param iv the initialization vector
  @return the cipher