Privacy Preserving Technologies and an Application to Public Transit Systems

In the first part of this talk, we present "Anonymous Credentials Light": the first provably secure construction of anonymous credentials that is based on the DDH assumption and can work in the elliptic group setting without bilinear pairings. Our construction requires just a few exponentiations in a prime-order group in which the DDH problem is hard, which makes it suitable for mobile devices, RFIDs and smartcards.

In the second part of the talk we explain how we can get secure e-cash with attributes from our construction and we show implementation results in an NFC enabled smartphone. The efficiency of our scheme is comparable to Brands e-cash, which is known to be the most efficient e-cash scheme in the literature but as a recently work of us shows it is impossible to prove it secure under the currently known techniques.