Challenge-response data communication protocol

A data communication technique facilitates the transmission of a data element in a trusted manner such that the receiver component can trust that the data element was not modified during the transmission. In addition, the receiver component is assured that the data element could only have been transmitted by a particular sender component. The data communication technique utilizes a challenge-response routine that ensures data integrity and non-repudiation. The data element is sent from the sender component to the receiver component during the challenge-response routine; in accordance with the example embodiment, the hashed response generated by the sender component is based upon the data element. The data communication technique can be implemented in the context of a single sign-on protocol that allows an authenticated user of a linking site to access protected resources associated with a linked web site without having to separately login to the linked web site.