Authors

David Derler (Graz University of Technology), Stephan Krenn (AIT Austrian Institute of Technology), Daniel Slamanig (Graz University of Technology)

Abstract

Redactable signature schemes allow to black out predefined parts of a signed message without affecting the validity of the signature, and are therefore an important building block in privacy-enhancing cryptography. However, a second look shows, that for many practical applications, they cannot be used in their vanilla form. On the one hand, already the identity of the signer may often reveal sensitive information to the receiver of a redacted message; on the other hand, if data leaks or is sold, everyone getting hold of (redacted versions of) a signed message will be convinced of its authenticity. We overcome these issues by providing a definitional framework and practically efficient instantiations of so called signer-anonymous designated-verifier redactable signatures (AD-RS). As a byproduct we also obtain the first group redactable signatures, which may be of independent interest. AD-RS are motivated by a real world use-case in the field of health care and complement existing health information sharing platforms with additional important privacy features. Moreover, our results are not limited to the proposed application, but can also be directly applied to various other contexts such as notary authorities or e-government services.

Venue

15th International Conference on Cryptology and Network Security, CANS 2016 (http://cans2016.di.unimi.it/)

Place and Date

Milan, Italy, November 14-16, 2016

Publication Reference

David Derler, Stephan Krenn, and Daniel Slamanig. “Signer-Anonymous Designated-Verifier Redactable Signatures for Cloud-Based Data Sharing“, in: Sara Foresti and Giuseppe Persiano (eds.) CANS 2016, pp. 211-227, LNCS 10052, Milan/Italy, Springer.

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