Blockchains, a decentralized peer-to-peer (P2P) ledger system, can provide trusted consensus, computation, and immutable data between untrusted entities. However, the privacy of blockchain is required, when applying blockchain technologies to various application environments (e.g., health, transportation, asset, and big data management, etc.). In this talk, I will first present a survey in generic non-interactive proofs including zk-SNARK (zero- knowledge Succinct Non-interactive Argument of Knowledge) and PCP (probability check proof) proof systems. Then we turn our attention to the applications of private computing in blockchain.

I will present our work on how to make transaction confidentially in supply chain management. We utilize non-interactive proofs of knowledge of elliptic curve discrete logarithms to present membership and verifiable encryption proof, which offers plausible anonymity when combined with the regular signing process of the blockchain transactions. The proof system requires no trusted setup, both its communication and computation complexities are linear in the number of set members, and its security relies on the discrete logarithm assumption. As a use-case for this scenario, we present Mesh which is a blockchain-based framework for supply chain management using radio frequency identification (RFID). The confidentiality of the transacted information is realized using a lightweight key chaining mechanism implemented on RFIDs. I will also show the experiments for evaluating the performance of the Mesh.