Reed is a transitive prefix authentication scheme (Meyer, 2023bb): given a sequence of events, we construct a directed acyclic graph (DAG), whose edges correspond to one object containing a secure hash of the other object (i.e., a Merkle-DAG). For each event, we assign a commitment vertex which has a path to the event, as well as paths to the commitment vertices of all earlier events. Given the commitment vertices of two events and the out-neighborhood of the path between them, we can reconstruct the hashes of all path vertices, thus proving that the first event did indeed happen before the other. Reed guarantees that the out-neighborhoods of these paths are small, i.e., verification is efficient.