What end-to-end encryption protects — and what it misses — is one of the most important distinctions in practical security. This is a technical breakdown. The Precise Definition End-to-end encryption (E2EE) means a message is encrypted on the sender's device, travels encrypted through all intermediaries, and is decrypted only on the recipient's device. No server in the path — not the service provider's infrastructure, not your ISP — can read the content. This is genuinely powerful. Even if Signal's servers are compromised, even if a government serves a lawful demand, even if your traffic is intercepted at a coffee shop — the message content is unreadable to anyone except the intended recipient. What it does not mean: using an E2EE app makes you private. These are different claims with a significant gap between them. How It Actually Works: The Signal Protocol Key Exchange (X3DH) Before two parties can exchange encrypted messages, they need to establish a shared secret without transmitting it.…