One-round zero-knowledge proofs and their applications in cryptographic systems

A zero-knowledge proof (ZKP) is an interactive proof between two parties: prover and verifier, where the prover proves the knowledge of a secret without revealing any information about the secret itself. ZKPs were first introduced in 1985 for identity verification systems and became powerful tools for many cryptographic applications. There has been a growing concern about the risk of identity theft in critical situations, like homeland security and e-commerce. ZKPs are the ideal solution to challenges in identification since they allow costumers to prove identities without exchanging sensitive information that may lead to identity theft. Other applications of ZKPs include smart cards, digital cash, anonymous communication, electronic wallets, electronic voting, multimedia security and digital watermarks. Existing ZKPs are iterative in nature; their protocols require multiple communication rounds between parties. Due to the cost of iteration, practitioners see ZKPs as unsuitable in practice and therefore develop other tools to avoid using ZKPs. The proposed approach creates new protocols that allow the prover to prove knowledge of a secret without revealing it. The new approach, called a one-round zero-knowledge-proof, meets all the requirements of ZKPs, yet runs in a single round. The new approach substantially reduces the running-time complexity and communications cost. It eliminates the iteration cost and makes such proofs suitable for practical cryptographic systems for both governmental and commercial applications. The focus of this dissertation is the theory of one-round ZKPs. It presents efficient and secure one-round ZKPs for several classical problems that are used in real life applications. It studies the performance of the proposed one-round ZKPs compared to the existing iterative ZKPs in terms of computation and communication costs. It presents a case study on an identity verification scheme that uses both the iterative ZKP and the new one-round ZKP to compare the results and show the advantages of the new approach.