CWI Cryptology Group

Abstract: We report on the first large-scale and practical application of multiparty computation, which took place in January 2008. Details are given on the background and motivation for the application, as well as on the actual system that was employed. We end with some thoughts on the future potential of multiparty computation in practice.

Abstract: There are many real-world situations, where there is much to be gained by having access to a trusted third party. Yet typically this is either expensive or even not possible at all. Multiparty computation (MPC) eliminate this dilemma by providing a virtual trusted third party, who performs the desired computation. Practical MPC is still in its infancy, yet has been shown feasible in real life. One interesting problem is that of solving linear programming (LP) problems. Such problems occurs naturally, e.g. in economics, which gives rise to a large number of motivating examples. A relatively simple yet feasible solution to this problem is presented. The secure computation has been implemented and solves (small) problem instances in a reasonable amount of time. This implementation provides a starting point for a discussion of the differences between theory and practice.

Abstract: Our privacy is put at risk as more and more of our daily transactions are done electronically and they all require one to reveal personal information without being able to control what for this data is used by whom. This is even made worse storing and mining data becomes ever easier. In this talk we will discuss how technology can help users to regain and retain control over their personal data. In particular, we will see how one can authenticate without identify oneself. We will conclude with a discussion of open problems.

Abstract: We take a step towards a more realistic modeling of personal digital signatures, where the human user, his mobile equipment, his PC and a server where he may have an account, are all considered as independent players in the protocol, and where only the human user is assumed incorruptible. We then propose a protocol for issuing digital signatures on behalf of the user. This protocol is proactively UC-secure assuming at most one player is corrupted in every operational phase. The protocol allows for mobile units with very small computing power by securely outsourcing computation to the PC and is also mobile in that it allows usage of any PC that can communicate properly. Finally, we report on the results of a prototype implementation of our solution. Joint work with Gert Mikkelsen