A February 3 paper written by Nikolai Durov, a co-founder of Telegram, describes the details of the consensus mechanism of Telegram Open Network, called Catchain. The proposed solution is a Byzantine Fault Tolerant (BFT) Proof of Stake (PoS) algorithm, similar to that used by NEO or Cosmos.
BFT algorithms are attempted solutions to solve the problem of Byzantine generals, where actors of a certain network must maintain functionality, even if some nodes are unreliable or harmful.
Catchain works as long as one third of the nodes is not harmful, which corresponds to the theoretical limit indicated for BFT solutions. The system focuses on validating each block when it is created, similar to Cosmos ’Tendermint or NEO’s dBFT. This is in contrast to systems proposed by Ethereum and Cardano, where blocks are easy to produce, but must then be reconciled via fork resolution.
Each new block is created via a block generation round, during which validators have a limited time to agree. If they do not do this, the block will be skipped.
Each validator has a clear role during a block voting procedure, with some creating the blocks, others proposing a block to vote, while the remaining nodes vote on the proposal. The roles are shifted with each new round, which must ensure the correctness of the procedure.
Telegram has no more than 100 validators for the main chain and 10-30 for each ‘shard chain’. According to tests conducted in 2018, a block can be generated every five seconds, following the complete consensus procedure each time.
For the most part, TON developers report that the system is comparable to that of Cosmos and Algorand. Differences lie in some of the details, such as how the nodes communicate with each other. Simply allowing each node to communicate with each other is very inefficient, meaning that every project tried to find its own way to make the process faster.
The SEC prevented the launch of TON with an emergency action submitted in October 2019. The committee argues that Telegram has carried out a non-sanctioned sale of securities.
Other ecosystem participants claim that since the sale was limited to authorized investors only, Telegram did nothing wrong.
The network is currently only active in testnet mode, so some have not stopped making blockchain explorers for it. The committee has nevertheless been very critical of its state of development, arguing that there are few current or planned applications for its GRAM tokens.