Cryptology ePrint Archive: Report 2015/076

Fully Structure-Preserving Signatures and Shrinking Commitments

Masayuki Abe and Markulf Kohlweiss and Miyako Ohkubo and Mehdi Tibouchi

Abstract: Structure-preserving signatures are schemes in which public keys, messages, and signatures are all collections of source group elements of some bilinear groups. In this paper, we introduce fully structure-preserving signature schemes, with the additional requirement that even secret keys should be group elements. This new type of structure-preserving signatures allows for efficient non-interactive proofs of knowledge of the secret key and is useful in designing cryptographic protocols with strong security guarantees based on the simulation paradigm where the simulator has to extract the secret keys on-line.

To gain efficiency, we construct shrinking structure-preserving trapdoor commitments. This is by itself an important primitive and of independent interest as it appears to contradict a known impossibility result. We argue that a relaxed binding property lets us circumvent the impossibility result while still retaining the usefulness of the primitive in important applications as mentioned above.

Category / Keywords: public-key cryptography / digital signatures

Original Publication (with major differences): IACR-EUROCRYPT-2015

Date: received 2 Feb 2015

Contact author: abe masayuki at lab ntt co jp

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Version: 20150210:203615 (All versions of this report)

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