International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 10 February 2015

Masayuki Abe, Markulf Kohlweiss, Miyako Ohkubo, Mehdi Tibouchi
ePrint Report ePrint Report
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.

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