Paper 2010/089

Interactive Locking, Zero-Knowledge PCPs, and Unconditional Cryptography

Vipul Goyal, Yuval Ishai, Mohammad Mahmoody, and Amit Sahai


Motivated by the question of basing cryptographic protocols on stateless tamper-proof hardware tokens, we revisit the question of unconditional two-prover zero-knowledge proofs for $NP$. We show that such protocols exist in the {\em interactive PCP} model of Kalai and Raz (ICALP '08), where one of the provers is replaced by a PCP oracle. This strengthens the feasibility result of Ben-Or, Goldwasser, Kilian, and Wigderson (STOC '88) which requires two stateful provers. In contrast to previous zero-knowledge PCPs of Kilian, Petrank, and Tardos (STOC '97), in our protocol both the prover and the PCP oracle are efficient given an $NP$ witness. Our main technical tool is a new primitive that we call {\em interactive locking}, an efficient realization of an unconditionally secure commitment scheme in the interactive PCP model. We implement interactive locking by adapting previous constructions of {\em interactive hashing} protocols to our setting, and also provide a direct construction which uses a minimal amount of interaction and improves over our interactive hashing based constructions. Finally, we apply the above results towards showing the feasibility of basing unconditional cryptography on {\em stateless} tamper-proof hardware tokens, and obtain the following results: *) We show that if tokens can be used to encapsulate other tokens, then there exist unconditional and statistically secure (in fact, UC secure) protocols for general secure computation. *) Even if token encapsulation is not possible, there are unconditional and statistically secure commitment protocols and zero-knowledge proofs for $NP$. *) Finally, if token encapsulation is not possible, then no protocol can realize statistically secure oblivious transfer.

Available format(s)
Publication info
Published elsewhere. Unknown where it was published
CryptographyStatistical SecurityZero KnowledgeInteractive ProofInteractive PCPCommitment SchemeOblivious TransferInteractive Hashing
Contact author(s)
mahmoody @ gmail com
2010-02-22: received
Short URL
Creative Commons Attribution


      author = {Vipul Goyal and Yuval Ishai and Mohammad Mahmoody and Amit Sahai},
      title = {Interactive Locking, Zero-Knowledge PCPs, and Unconditional Cryptography},
      howpublished = {Cryptology ePrint Archive, Paper 2010/089},
      year = {2010},
      note = {\url{}},
      url = {}
Note: In order to protect the privacy of readers, does not use cookies or embedded third party content.