Which Durov brother created the MTProto protocol for Telegram?

Nikolai Durov created the MTProto protocol for Telegram. A mathematician and programmer, he worked with his brother Pavel Durov to build Telegram, with Nikolai responsible for much of the technical and cryptographic design while Pavel supplied leadership, financing, and infrastructure.

MTProto is Telegram's proprietary communications protocol for transporting and protecting data between clients and servers. It was designed for multi-device messaging, fast delivery, and operation across different network conditions. Telegram has published technical descriptions of successive MTProto versions, while its secret chats add a separate end-to-end-encryption design.

The brothers' roles are often blurred because both are described as Telegram co-founders. Pavel is the public face and business leader, whereas Nikolai is the credited protocol designer. Axel Neff and Ilya Perekopsky have held Telegram-related executive or operational roles, but neither is the Durov brother associated with MTProto's creation.