code: public InputStream decryptStream(InputStream input) throws SymmetricKeyException {
          try {
              EncryptedInputStream encryptedInputStream = new EncryptedInputStream(input);
              byte[] iv = encryptedInputStream.getIv();
              Cipher cipher = getCipher(Cipher.DECRYPT_MODE, iv);
              return new CipherInputStream(encryptedInputStream, cipher);
          } catch (IOException e) {
              throw new SymmetricKeyException(e);
          }
      }
docs: Decrypt the input stream. The encrypted stream must be prefixed with the IV header
  (16 bytes) use when encrypting the data of the given input stream.
  @param input InputStream of the data to be decrypted
  @return InputStream of the decrypted data
  @throws SymmetricKeyException