2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33272A secure reliable multicast protocol enables a process to send a message to a group of recipients such that all correct destinations receive the same message, despite the malicious efforts of fewer than a third of the total number of processes, including the sender. This has been sh own to be a useful tool in building secure distributed services, albeit with a cost that typically grows linearly with the size of the system. For very large networks, for which this is prohibitive, we present two approaches for reducing the cost: First, we show a protocol whose cost is on the order of the number of tolerated failures. Secondly, we show how relaxing the consistency requirement to a probabilistic guarantee can reduce the associated cost, effectively to a constant.preprint of a paper to appear in the Distributed Computing JournalCryptography and SecurityDistributed, Parallel, and Cluster Computingc.2.0;c.2.4;c.4text