Telegram Calls in IranTelegram
Last Thursday, we finished rolling out free End-to-End Encrypted Voice Calls to all Telegram users around the world.
On April 16, Iranian providers – both mobile operators and home internet providers – started blocking Telegram calls. According to the news agencies, 20 providers received a judicial order from the Attorney General to do this.
On Telegram's side, calls are enabled and working for the entire world, including Iran. But internet providers in the country are blocking the protocol that is used to establish a connection between users before a P2P call can be activated.
Why are they blocking calls?
We did not receive any communications regarding the reasons, so we have no idea what could stand behind the decision. However, the fact that other VoIP providers in the country are still operating normally clearly suggests that this move is targeting Telegram specifically.
Can I use calls in Iran at all?
Even though Telegram Calls use End-to-End encryption and you can communicate via P2P, your app still needs to contact the server using the UDP protocol to establish the initial connection for each call. This makes it technically possible for a provider to block access to calls (although of course, they can't see your data).
For now, both you and your partner need to use encrypted VPNs to go around such filtering (OpenVPN, Lantern, and Hotspot shield have been confirmed to work, but there are countless others). Please note that it's important that both VPN providers must encrypt UDP traffic as well.
If one of you is using a VPN that doesn't encrypt UDP traffic, your internet provider can analyze the packets, understand that they belong to a Telegram call, and stop them. In this case, the call won't work, even though the providers can't know what you said or who you called.