Techniques described herein can be utilized to implement a protocol for performing an unbiased selection of a particular worker node among a plurality of worker nodes to execute a computational task. Nodes of a distributed network may register to join a group membership by generating quantities derived at least in part from a hierarchical data structure, such as an accumulation tree, whose parameters are defined by a manager node. The manager node may utilise the quantities provided by the plurality of worker nodes to perform an unbiased selection of a worker node from among the plurality of worker nodes to perform a computational task. The invention is particularly suited, but not limited to, for use in a blockchain network such as Bitcoin. In at least some cases, the manager node cannot determine, based on quantities supplied by the worker nodes, whether a particular worker node was selected to perform the computational task.