Authors:
Julien Bringer
1
and
Alain Patey
2
Affiliations:
1
Morpho and Safran Group, France
;
2
Morpho, Safran Group and Télécom ParisTech, France
Keyword(s):
Group Signatures, Verifier-Local Revocation, Backward Unlinkability, Efficiency, Revocation Check.
Related
Ontology
Subjects/Areas/Topics:
Applied Cryptography
;
Cryptographic Techniques and Key Management
;
Data and Application Security and Privacy
;
Data Engineering
;
Databases and Data Security
;
Information and Systems Security
;
Privacy
Abstract:
Verifier-Local Revocation (VLR) group signatures are a particular case of dynamic group signature schemes where the revocation process does not influence the activity of the signers. The verifiers use a Revocation List and in all known schemes, checking a signature requires a computational time linear in the number of revoked members. Usually, it requires one pairing per revoked user. Recently, Chen and Li proposed a scheme where Revocation Check uses exponentiations instead of pairings. In this paper, we first propose a correction of their scheme to enable a full proof of the traceability property and we succeed with a constant additional cost only to extend this tweaked scheme to ensure Backward Unlinkability (BU). This important property prevents the loss of anonymity of past signatures when a user is revoked. We thus obtain the scheme with the most efficient Revocation Check among VLR schemes enabling BU.