Byzantine agreement is a fundamental issue in fault-tolerant and secure distributed computing. Protocols solving Byzantine agreement guarantee that a sender can transmit a value to a group of receivers consistently, even if some of the nodes, including the sender, are arbitrarily faulty. In the past, protocols for Byzantine agreement were generally either authenticated or non-authenticated. Non-authenticated p r otocols make no use of signatures, while in authenticated protocols, all messages

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... ve to be signed. Authenticated protocols can tolerate more faults and are m o r e message-e cient than non-authenticated protocols, but they have the disadvantage of timeconsuming signature generation. In this paper, we introduce t e chniques to reduce the amount of signatures by combining mechanisms from authenticated and nonauthenticated p r otocols.