LazyTower is a data structure for proof of membership. It is a low-gas alternative to on-chain Merkle trees. The amortized cost for adding an item is O(1). (99424 gas for W=4, including 21000 and the event cost) The cost for ZK proving is O(1). The cost for non-ZK proving is O(log(N)). The Core Idea Level full => hash (digest)

Background membershipMap Merkle TreeIncremental Binary Tree RSA Accumulator gas HashTower Amortized cost: O(1)