The present disclosure provides a computer-implemented method, computer system and computer program product for authentication. The computer-implemented method comprises sending an image to a device, where the image is adapted to be classified to a first category by an image classifier, and where the first category is different from an actual category of the image; receiving a response message from the device, where the response message indicates a second category of the image determined by the device; and determining the device to be an authorized device in response to the second category being consistent with the first category.