DGM: A Dynamic and Revocable Group Merkle Signature

Abstract

Group signatures are considered as one of the most prominent cryptographic primitives to ensure privacy. In essence, group signatures ensure the authenticity of messages while the author of the message remains anonymous. In this study, we propose a dynamic post-quantum group signature (GS) extending the static G-Merkle group signature (PQCRYPTO 2018). In particular, our dynamic G-Merkle (DGM) allows new users to join the group at any time. Similar to G-Merkle scheme, our DGM only involves symmetric primitives and makes use of a One-Time Signature scheme (OTS). Each member of the group receives a certain amount of OTS key pairs and can ask the Manager M for more if needed. Our DGM also provides an innovative way of signing revocation by employing Symmetric Puncturable Encryption (SPE) recently appeared in (ACM CCS 2018). DGM provides a significantly smaller signature size than other GSs based on symmetric primitives and also reduces the influence of the number of group members on the signature size and on the limitations of the application of G-Merkle.