Flexible Fair and Collusion Resistant Pseudonym Providing System

In service providing systems, user authentication is required for different purposes such as billing, restricting unauthorized access, etc., to protect the privacy of users, their real identities should not be linked to the services that they use during authentication. A good solution is to use pseudonyms as temporary identities. On the other hand, it may also be required to have a backdoor in pseudonym systems for identity revealing that can be used by law enforcement agencies for legal reasons. Existing systems that retain a backdoor are either punitive (full user anonymity is revealed), or they are restrictive by revealing only current pseudonym identity of. In addition to that, existing systems are designed for a particular service and may not fit into others. In this paper, we address this gap and we propose a novel pseudonym providing and management system. Our system is flexible and can be tuned to fit into services for different service providers. The system is privacy-preserving and guarantees a level of anonymity for a particular number of users. Trust in our system is distributed among all system entities instead of centralizing it into a single trusted third party. More importantly, our system is highly resistant to collusions among the trusted entities. Our system also has the ability to reveal user identity fairly in case of a request by law enforcement. Analytical and simulation based performance evaluation showed that Collusion Resistant Pseudonym Providing System (CoRPPS) provides high level of anonymity with strong resistance against collusion attacks