1. An interactive method for authentication of a client, comprising: storing data defining a graphical representation ( 4010 ) 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 ( 1040 ) associated with the client in a memory, the data set including a first shared secret and a second shared secret, the first shared secret ( 4051 , 4052 , FIG. 5D-2 ) 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 ( 8100 ) comprising data identifying a second plurality of the pre-defined locations on the frame of reference; receiving via a first data communication ( 2040 ), a client identifier ( FIG. 3B 3040 ) from the client and initiating an authentication session; presenting via a second data communication ( 2050 ), to the client an instance ( 8060 ) 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 ( 8040 ) from the client via a third data communication ( 2060 ), the input data including characters entered by the client using an input device; and determining ( 2070 ) whether the input data matches the response pointed to by the challenge.