International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Multi-Trapdoor Commitments and their Applications to Non-Malleable Protocols

Rosario Gennaro
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Abstract: We introduce the notion of multi-trapdoor commitments which is a stronger form of trapdoor commitment schemes. We then construct two very efficient instantiations of multi-trapdoor commitment schemes, based on the Strong RSA Assumption and the recently introduced Strong Diffie-Hellman Assumption. The main applications of our result are non-malleable trapdoor commtiments and a compiler} that takes any proof of knowledge and transforms it into one which is secure against a concurrent man-in-the-middle attack. Such a proof of knowledge immediately yields concurrently secure identification protocols. When using our number-theoretic istantiations, the non-malleable commitment and the compiler are very efficient (require no more than four exponentiations). The latter also maintains the round complexity of the original proof of knowledge; it works in the common reference string model, which in any case is necessary to prove security of proofs of knowledge under this kind of attacks. Compared to previously known efficient solutions, ours is a factor of two faster.
  title={Multi-Trapdoor Commitments and their Applications to Non-Malleable Protocols},
  booktitle={IACR Eprint archive},
  keywords={cryptographic protocols / zero-knowledge, concurrency, authentication},
  note={Preliminary version in Crypto 2004 12748 received 7 Oct 2003, last revised 26 Nov 2004},
  author={Rosario Gennaro},