Privacy-preserving alibi systems

An alibi provides evidence of a person's past location and can be critical in proving ones innocence. An alibi involves two parties: the owner, who benefits from the alibi, and the corroborator, who testifies for the owner. As mobile devices become ubiquitous, they can determine where we are and what we are doing, and help us to establish evidence of our location as they accompany us on our daily activities. Existing location-based services like Google Latitude can already track and record our every move, but these systems require us to reveal our identity when recording our location. This leaves our privacy at risk, and requires a trusted third party to maintain our location information.