ZK Email

ZK Email is a project that uses zero-knowledge proofs to let people prove facts from their email, such as receiving a message from a given domain or owning a Twitter account, without revealing the rest of the email. The article explains that DKIM signatures already attached to most emails since 2017 can serve as a verifiable source of data, and that zero-knowledge circuits address three problems of posting this on-chain: calldata cost, controllable privacy, and verification cost. Its technical contributions include an arbitrary-length SHA256 circuit, a method that hashes most of the message outside the proof, and regex matching via deterministic finite automata compiled into Circom. The team says its MIT-licensed repositories have been used by applications such as zkp2p, emailwallet, and nozee.