1. An interactive method for authentication of a client, comprising: storing data defining a graphical representation of a frame of reference adapted for rendering on a display, the frame of reference including a number N of pre-defined locations in the frame of reference having coordinates on the frame of reference; storing a data set associated with the client in a memory, the data set including a first shared secret and a second shared secret, the first shared secret comprising data identifying a first plurality of the pre-defined locations defining an ordered path on the frame of reference, and the second shared secret comprising data identifying a second plurality of the pre-defined locations on the frame of reference; receiving via a first data communication, a client identifier from the client and initiating an authentication session; presenting via a second data communication, to the client an instance of the graphical representation of the frame of reference in response to the request for use in the authentication session, including composing the instance by positioning characters in the number N of pre-defined locations according to a pattern different than used in other authentication sessions with the client, the characters consisting of members of a character set including M members, where N is greater than 2M, and in which characters in the second plurality of pre-defined locations identified by the second shared secret comprise a challenge pointing to pre-defined locations on the ordered path in which characters comprising a response are positioned in the instance; accepting input data from the client via a third data communication, the input data including characters entered by the client using an input device; and determining whether the input data matches the response pointed to by the challenge and if the input data matches, signaling successful authentication, and if the input data does not match, signaling failed authentication.