A security processing element stores authentication data corresponding to a plurality of possible authentication modes. At a time of activation, the security processing element randomly selects one of the authentication modes for presentation to the user. The user must successfully enter data corresponding to the randomly selected authentication mode. In an alternative embodiment, the security processing element can randomly select a plurality of authentication modes that are sequentially presented to the user. The user must successfully respond to each of the plurality of requested authentication modes. In another embodiment, for high security communications, the security processing element may select from a subset of authentication modes that are considered to be more robust. Conversely, the security processing element may select from a subset of randomly presented authentication modes that are considered less robust when used in a low security setting.