A method to authenticate a server to a client is provided, including in-band and out-of-band techniques. At least a first shared secret identifies a server path, including a plurality of pre-defined locations on a frame of reference (e.g. a grid). An authentication session is initiated upon receiving a client identifier at the server-side resources. A current session instance of the grid is presented to the client, populated with characters. The process includes sharing between the client and the server a challenge identifying a random subset of the plurality of predefined locations in the server path, and a response including characters that match the characters in the locations on the server path identified by the challenge. As a result, client is capable of verifying that the server has access to the first shared secret. Then a protocol is executed to authenticate the client to the server.