In
cryptographic literature, the word "byzantine" is used to describe participants in some sort of
protocol who have malicious intentions. Ideally, a distributed protocol, e.g. for
authenticitation should provide scurity even when some of the participants are actively trying to sabotage the protocol.
The expression was coined by Leslie Lamport in an article in the ACM Transactions on Programming Languages and Systems, titled "The Byzantine Generals Problem." In it, he described a situation of Byzantine troops laying siege on a city. They want to decide when to attack, but they know that there are traitors among them. A traitor could create fake messages to try and make different parts of the army attack at different times, which would put them at a great disadvantage.
Lamport proved that it's impossible to prevent the sabotage if more than 1/3 of the generals are traitors.