code: public byte[] decrypt(byte[] iv, byte[] cipherText) throws RuntimeException {
  
          AEADParameters aeadParams = new AEADParameters(
                  new KeyParameter(key), TAG_LENGTH,
                  iv,
                  authData);
  
          cipher.init(false, aeadParams);
          byte[] buffer = newByteArray(cipherText);
          byte[] plainText = newBuffer(cipher.getOutputSize(cipherText.length));
          int outputOffset = cipher.processBytes(buffer, 0, buffer.length, plainText, 0);
  
          try {
              cipher.doFinal(plainText, outputOffset);
          } catch (InvalidCipherTextException e) {
              throw new RuntimeException("Error: ", e);
          }
  
          return plainText;
      }
docs: Given the iv, decrypt the provided data
  
  @param iv         initialization vector
  @param cipherText data to be decrypted
  @return byte array with the plain text
  @throws RuntimeException