Shrubs - A New Gas Efficient Privacy Protocol (Devcon5)

Fri, Oct 2, 2020, 12:00 AM

Visit the https://archive.devcon.org/ to gain access to the entire library of Devcon talks with the ease of filtering, playlists, personalized suggestions, decentralized access on IPFS and more. https://archive.devcon.org/archive/watch/5/shrubs-a-new-gas-efficient-privacy-protocol ERC20 tokens that offer high levels of privacy to their users have been a longtime goal in the Ethereum ecosystem. To implement a privacy protocol that offers very strong privacy guarantees such as those of Zcash, it's necessary to maintain a large Merkle tree of commitments. Unfortunately, doing so in a smart contract can be expensive. For example, to support the same number of total transactions as Zerocash (2^64), one would require a tree depth of 64, and thus 64 storage updates per transaction, which is prohibitively expensive gas-wise. In this work, we introduce a new Merkle tree variant, which is defined not by the root, but by the path to the rightmost non-empty leaf node (or frontier), in a tree filled from left to right. This allows commitments to be inserted with O(1) amortized updates, at the expense of a slightly more complicated zk-SNARK proof, used to prove that the commitment is in the tree. We use this new data structure to create ShrubsToken, a new gas efficient privacy token, with Zcash-like privacy. Based on our experiments, we estimate that Shrubs will use around 500,000 gas per transaction, after the next Ethereum hard fork. Speaker(s): Alex Gluchowski, Kobi Gurkan, Marek Olszewski, Eran Tromer, Alexander Vlasov Skill level: advanced Track: Privacy Keywords: technical Follow us: https://twitter.com/efdevcon, https://twitter.com/ethereum Learn more about devcon: https://www.devcon.org/ Learn more about ethereum: https://ethereum.org/ Devcon is the Ethereum conference for developers, researchers, thinkers, and makers. Devcon 5 was held in Osaka, Japan on Oct 8 - 11, 2019. Devcon is organized and presented by the Ethereum Foundation, with the support of our sponsors. To find out more, please visit https://ethereum.foundation/