We present hamm, a Haskell library that enables programmers to easily configure authenticated map (key-value store) implementations. We use type level programming techniques to establish an extensible foundation, and provide an example base map and several example “add on” transformers supporting features such as caches, Bloom filters and paging structures. Another add-on enables a prover to provide a “summary” containing only small a subset of the map’s data, and a verifier to subsequently receive and verify additional data only if needed. We present preliminary performance results demonstrating significant potential for authenticated maps configured using hamm to support our goal of enabling participants to join blockchain networks faster.