IACR News item: 10 February 2015
Masayuki Abe, Markulf Kohlweiss, Miyako Ohkubo, Mehdi Tibouchi
ePrint Reportpublic 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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