TLS would normally be used between the client and server. Viber may use TLS for that too, though WhatsApp and Signal use Noise pipes for that purpose. The point

TLS would normally be used between the client and server. Viber may use TLS for that too, though WhatsApp and Signal use Noise pipes for that purpose. The point of end to end encryption is that they're also encrypting the messages so that they can't be read on the server. Don't know what Viber is using, but moxie posted a link to the details about WhatsApp's implementation. https://www.whatsapp.com/security/WhatsApp-Security-Whitepaper.pdf https://www.whatsapp.com/security/WhatsApp-Security-Whitepap...