A Robust Verifiably Encrypted Signature Scheme

Sae-Ran Kwon, Sangho Lee

Peidong Guan, Shuai Wang

Abstract Verifiably encrypted signature (VES) schemes are extensively utilized in fair exchange which combine the features of encryption and signature, aiming to provide a solution that can not only verify the validity of signatures but also safeguard the privacy of signatures. With the development of quantum algorithms and quantum computing, it is necessary to construct a VES protocol that can resist attack of quantum computing. At the same time, some new security properties can also be added to the VES protocol to enhance its security. To reach this goal, we propose a state-of-the-art lattice-based verifiably encrypted group signature (VEGS) scheme. In the random oracle model, the VEGS scheme is provably secure under the assumptions of learning with error (LWE) and inhomogeneous small integer solution (ISIS). Our scheme provides five security properties, namely unforgeability, opacity, extractability, anonymity and traceability. The three properties unforgeability, opacity and extractability are the properties that the VES protocol needs to meet, and the anonymity and traceability properties are additional security properties brought by combining with the group signature.

Martianus Frederic Ezerman, Hyung Tae Lee, San Ling +2 more

David Chaum, Saw Sandra Roijakkers

Li Yong-qiang, Xin Xiang-jun

Recently, a randomized verifiably encrypted signature scheme without random oracle is proposed by Yang et al. However, according to the security analysis, it is found that given two signatures on a message, the adversary can forge a new signature on the same message. Therefore, their scheme has not the propriety of undenibility, which means that their scheme is insecure. Because a verifiably encrypted signature scheme is mainly used to construct the optimistic fair exchange protocols, it should have the strong unforgerity.

Ryan Amiri