This article takes a technical look at the subject of messengers and explains the various factors that contribute to the overall security of a messenger. Instead of looking at individual messengers, the basic functionality of modern messengers is explained, the communication protocols used in this context and their security properties are presented, and other aspects that play a role in the secure use of a messenger are mentioned, including data protection aspects in particular. The aim is to provide interested readers with comprehensive information on the topic of 'secure messengers' and to enable them to subsequently assess the security of a messenger themselves on the basis of publicly available information.
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