How to capture Telegram Desktop app traffic using Fiddler Classic

[Rip8]

Using Fiddler, is it possible to monitor the traffic of the Telegram Desktop application in order to auto-save messages/photos/videos to local storage as they are received?

 

I know that it is possible to do this using the telegram API, but for the educational purpose of studying traffic monitoring through Fiddler, I would like to explore this unusual approach.

[Nick Iliev]

Hello,

 

Fiddler Everywhere and Fiddler Classic are HTTPS proxies, and as such they can capture application traffic that utilizes HTTP, HTTPS, WebSocket, or gRPC protocols. While some basic operations in the Telegram desktop application use HTTP (pre-handshake requests), all communication is end-to-end encrypted. The encryption is not using the TLS protocol that is widely used with HTTP, but instead, Telegram created its encryption protocol called MTProto. The creators of Telegram started this protocol with the sole idea of preventing traffic decryption from the intermediate. 

All of the above considered, Fiddler, as an HTTP(S) proxy, won't be able to capture and decode the messages sent and received from the desktop Telegram application.

More on how Telegram works and what MTProto stands for can be found here: https://core.telegram.org/techfaq#q-why-did-you-go-for-a-custom-protocol 

 

 

Regards,
Nick Iliev
Progress Telerik

[Rip8]

Thank you very much for your kindness in writing such a detailed answer.