Telegram co-founder Nikolai Durov described the operation scheme of the Catchain Consensus Protocol algorithm that underlies the Telegram Open Network (TON) blockchain platform.

Catchain is a Byzantine Fault Tolerant (BFT) algorithm, that is, it supports the functionality of the network even in cases where some of its nodes are unreliable or malicious. Catchain will work as long as a third of the nodes remains reliable, which is equivalent to the theoretical limit set for BFT solutions.

The protocol checks each newly generated block. If validators do not validate a block in a limited amount of time, Catchain will not let it to the network.

In order to guarantee the correctness of voting on the blocks, the validators nominating blocks for voting and the voting validators change their roles with each new round.

It is expected that the TON blockchain will have a maximum of 100 validators for the masterchain and from 10 to 30 for each shardchain. According to tests carried out in 2018, a block can be generated every five seconds, passing the procedure of full coordination.

Closed testing of the TON platform started in April 2019. Access to the test version was given to several professional teams consisting of blockchain developers from around the world, including Russia.

However, the official launch of the project has been postponed due to a lawsuit against the company by the US Securities and Exchange Commission (SEC).