In 2001, Zooko Wilcox-O'Hearn conjectured that a key value system, in the way the keys address those values, must make a compromise between three properties. Those properties are:
Since WhatsApp announced its acquisition, a lot of people started to switch to alternatives, trying to escape from Facebook. Some of them then discovered my article about Telegram, and a common answer was "hey, at least, it is better than WhatsApp, because it is open source, faster and it has encryption".
Following the previous article, people have asked me what I would consider as a good secure system, and others asked me to review their app, so I think it will be interesting to expose my process when studying those projects.