Store a Merkleised state of any kind of data for the entire set of Ethereum addresses efficiently! This KV storage is backed by a sparse Merkle tree, which has a depth of 160. An Ethereum address is interpreted as a number and used as the index for each leaf. In addition to membership proofs as in regular Merkle teres, it's also possible to prove non-membership!
Implementation of an efficient sparse Merkle tree as described by Vitalik in https://ethresear.ch/t/optimizing-sparse-merkle-trees/3751
account storage repo: https://github.com/kevincharm/account_kv_storage_fe
smt library repo: https://github.com/kevincharm/smt_fe
running the code: fe test