Event Details
Unlinkable Policy-Based Sanitizable Signatures
Presenter: Ismail Afia
Supervisor:
Date: Wed, April 2, 2025
Time: 15:00:00 - 15:45:00
Place: Zoom - see below.
ABSTRACT
Abstract:
In CT-RSA 2020, P3S was proposed as the first policy-based sanitizable signature scheme, allowing the signer to designate future message sanitizers by defining an access policy relative to their attributes rather than their keys. However, since P3S utilizes a policy-based chameleon hash (PCH), it does not achieve unlinkability, a required notion in privacy-preserving applications. Moreover, P3S requires running a procedure to share the secret trapdoor information for PCH with each new sanitizer before sanitizing a new message. We further observe that to maintain transparency in P3S’s multiple sanitizers setting, the signature size should grow linearly with the number of sanitizers. In this work, we propose an unlinkable policy-based sanitizable signature scheme (UP3S) where we employ a rerandomizable digital signature scheme and a traceable attribute-based signature scheme as its building blocks. Compared to P3S, UP3S achieves unlinkability, does not require new secrets to be shared with future sanitizers prior to sanitizing each message, and has a fixed signature size for a given sanitization policy. We define and formally prove the security notions of the generic scheme, propose an instantiation of UP3S utilizing the Pointcheval-Sanders rerandomizable signature scheme and DTABS traceable attribute-based signature scheme, and analyze its efficiency. Finally, we compare UP3S with P3S in terms of the features of the procedures, scalability, and security models.
Location: Remote via Zoom
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Meeting ID: 824 7528 1212
Password: 904774
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