Verifiable encryption, group encryption, and their applications to separable group signatures and signature sharing schemes. Technical Report TR 260, Institute for Theoretical Computer Science, ETH Zürich, 1997. Proof systems for general statements about discrete logarithms. A graduate course in applied cryptography, 2020. In Moti Yung, Yevgeniy Dodis, Aggelos Kiayias, and Tal Malkin, editors, PKC 2006, volume 3958 of LNCS, pages 207-228. Curve25519: New Diffie-Hellman speed records. In Henri Gilbert and Helena Handschuh, editors, FSE 2005, volume 3557 of LNCS, pages 32-49.

The poly1305-AES message-authentication code. IEEE Computer Society Press, October 1997. A concrete security treatment of symmetric encryption. Mihir Bellare, Anand Desai, Eric Jokipii, and Phillip Rogaway.

Gligor, and Moti Yung, editors, ACM CCS 2013, pages 1087-1098.

Foteini Baldimtsi and Anna Lysyanskaya.

In Marc Fischlin and Jean-Sé bastien Coron, editors, EUROCRYPT 2016, Part II, volume 9666 of LNCS, pages 822-851. Automated unbounded analysis of cryptographic constructions in the generic group model.

Miguel Ambrona, Gilles Barthe, and Benedikt Schmidt.

Because encryption, authentication, and the associated proofs of knowledge are all instantiated in G the system is efficient, even for large groups. This enables us to encrypt group data using an efficient Elgamal-like encryption scheme, and to prove in zero-knowledge that the encrypted data is certified by a credential. The benefit of the new KVAC is that attributes may be elements in G, whereas previous schemes could only support attributes that were integers modulo the order of G. Members of the group authenticate to the server in a way that reveals only that they correspond to some encrypted entry, then read and write the encrypted entries.Īuthentication in our design uses a primitive called a keyed-verification anonymous credential~(KVAC), and we construct a new KVAC scheme based on an algebraic MAC, instantiated in a group G of prime order. In the proposed solution, a central server stores the group membership in the form of encrypted entries. The goal is to support private groups where membership information is readily available to all group members but hidden from the service provider or anyone outside the group. In this paper we present a system for maintaining a membership list of users in a group, designed for use in the Signal Messenger secure messaging app.

Signal messenger group