Telegram Secret Chat
Telegram's E2EE mode — opt-in, device-specific (not shown on other logged-in devices). Self-destruct timer, no forwarding allowed. Default Telegram chat is ONLY client-to-server encrypted.
Criticism: E2EE should be default like Signal/WhatsApp. Telegram founder Pavel Durov defends with "user choice + UX wins". Skeptics point to the custom MTProto protocol (not peer-reviewed like the Signal Protocol). Secret Chats don't exist for groups — only 1:1. Notable leak 2024: Cellebrite could extract regular Telegram chats from seized phones but not Secret Chats. Practical takeaway: use Signal for real security needs.