Silentium is a peer-to-peer (P2P) messaging application, meaning communication happens directly between you and your contact. No external servers receive your messages. In addition, it uses end-to-end RSA encryption (E2EE) to prevent third-parties from intercepting and reading your messages.
Disclaimer: as a P2P app, your IP Address could be exposed to your contact.
Your SilentiumID is uniquely generated everytime you open the app. Likewise, the ID of your contact changes. Neither contacts nor messages are saved anywhere.
Disclaimer: due to the temporary nature, it is possible for someone to have the same SilentiumID as you in the future. This doesn't necessarily mean anything bad, unless someone tries contacting that ID expecting to reach you.
The P2P nature of this app allows for it to be used at no cost.