http://qojbkchhyiihpj4yr3jewit2crirvzto7vd5t67m4bsumu52x3txomid.onion/safety.php
Limitation: Less user-friendly, both parties must be online at the same time. Session – Open-source, onion-routed traffic, no phone number required. Limitation: Smaller user base, still a relatively new project. Signal over Tor – Strong encryption, highly trusted, widely used.