Hard Invalidation of Electronic Signatures
            
                    Lucjan Hanzlik, Miroslaw Kutylowski, 
               Faculty of Fundamental Problems of Technology,
                  Wroclaw University of Technology, Poland

                                Moti Yung
                   Google Inc. and Columbia University, USA

We present a new concept for invalidating electronic signatures which, in many situations, 
seem to be better suited for real business and society applications. We do not rely on 
an administrative invalidation process executed separately for each single signing key 
and based on certificate revocation lists. Instead, all signatures created with a certain 
group are invalidated by a certain event. We propose a hard invalidation via releasing 
of the inherent cryptographic proof value – instead of soft invalidation via revoking 
certificates which leaves intact the cryptographic strength of signatures (even if legal 
validity is partially lost).

We present concrete efficient realizations of our ideas based on verifiable encryption, 
trapdoor discrete logarithm groups and ring signatures.

Keywords: electronic signature, revocation, deniability, verifiable encryption,
trapdoor discrete logarithm, ring signature.

paper presented at ISPEC'2015
published in LNCS 9065, Springer Verlag
DOI: 10.1007/978-3-319-17533-1_29