Redactable Signature with Compactness from Set-Commitment

TL;DR

This paper introduces an efficient redactable signature scheme that maintains compactness regardless of message size by combining set-commitment techniques with digital signatures, avoiding reliance on idealized models.

Contribution

It presents a novel redactable signature construction that achieves constant-size signatures independent of message length, using set-commitment and digital signatures without relying on the random oracle or generic group models.

Findings

Signature size is constant regardless of message length

The scheme is efficient and practical for real-world applications

Avoids reliance on idealized cryptographic assumptions

Abstract

Redactable signature allows anyone to remove parts of a signed message without invalidating the signature. The need to prove the validity of digital documents issued by governments is increasing. When governments disclose documents, they must remove private information concerning individuals. Redactable signature is useful for such a situation. However, in most redactable signature schemes, to remove parts of the signed message, we need pieces of information for each part we want to remove. If a signed message consists of l elements, the number of elements in an original signature is at least linear in l. As far as we know, in some redactable signature schemes, the number of elements in an original signature is constant, regardless of the number of elements in a message to be signed. However, these constructions have drawbacks in that the use of the random oracle model or generic group model. In this paper, we construct an efficient redactable signature to overcome these drawbacks. Our redactable signature is obtained by combining set-commitment proposed in the recent work by Fuchsbauer et al. (JoC 2019) and digital signatures.