The invention relates to distributed ledger technologies such as consensus-based blockchains. Computer-implemented methods for locking and unlocking transaction inputs and outputs are described. The invention is implemented using a blockchain network, which may be, for example, a Bitcoin blockchain. A group of entities form a group in with membership may be proven using an accumulation tree. A variety of methods are described for generating the accumulation tree, including methods that use a central authority and methods that use a decentralized protocol in place of the central authority. In various implementations, parties are able to unlock transaction outputs that are based on group membership without revealing their identity generally.