Toward succinct proofs of solvency
A firm that holds a large amount of crypto-assets on behalf of customers, such as a centralized exchange, can provide some level of assurance to their users by issuing frequent zero-knowledge proofs (ZKPs) of solvency (or reserves). These protocols have been studied for years, open problems remain.
Crypto-assets like BTC or ETH are governed by public key cryptography in a particular setting (secp256k1) that lacks a key feature (bilinear pairings) necessary for many modern, succinct ZKPs. Related work often considers only liabilities (not assets), or it resorts to implementing secp math into the circuit of a general zk-SNARK. Here, Jeremy Clark (Concordia) offers a new proof of solvency that directly covers both assets and liabilities in the poly-iop model (implemented over bls12-381), the “glue” that makes it work for assets on secp blockchains. Ultimately, the protocol is not succinct, but the non-succinct parts are manageable: the “gluing” protocol is largely a one-time pre-computation, and the “spill-over” from the large data sizes results in a proof that is linear in the number of bits used to capture an account balance, while remaining independent of (succinct in) the number of accounts (up to 4 billion accounts).
About the presenter:
Jeremy is an associate professor at the Concordia Institute for Information Systems Engineering. At Concordia, he holds the NSERC/Raymond Chabot Grant Thornton/Catallaxy Industrial Research Chair in Blockchain Technologies. He earned his PhD from the University of Waterloo, where his gold medal dissertation focused on designing and deploying secure voting systems including Scantegrity. Beyond research, he has worked with several municipalities on voting technology and testified to both the Canadian Senate and House finance committees on Bitcoin.
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