A method for authorizing access to a first computing device is provided. The method comprises the first computing device forming a challenge, encoding the challenge into a symbol, and displaying the symbol. The first computing device receives a request for access from a user. Access to the first computing device is allowed in response to provision of an access code to the first computing device by the user. The access code is formed by a server in response to capturing the symbol, decoding the symbol into the challenge, forming a request from the challenge, and providing the request to the server. The server forms a decision to allow access by the user to the first computing device.