Example implementations relate to authentication using a sequence of images. For example, a computing device may include an input device to receive data from a user and a processor in communication with the input device. The processor provides a request for a private key associated with the user, where the request includes a public key specifying a set of categories each relating to an object. The processor receives, via the input device, the private key in response to the request, where the private key includes a sequence of images based on the public key. The processor authenticates the user when each image in the sequence of images is associated with a particular object previously assigned to the user based on the set of categories.