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Tendermint and CometBFT

By Satya Nayak

Created in 2014, Tendermint (opens new window)accelerates the development of distinct blockchains with a ready-made networking and consensus solution, so developers do not have to recreate these features for each new case. You may already use Tendermint without being aware of it.

Tendermint modules attend to consensus and networking, which are important components of any blockchain. This frees developers to focus on the application level without descending into lower-level blockchain concerns such as peer discovery, block propagation, consensus, and transaction finalization. Without Tendermint, developers would be forced to build software to address these concerns, which would add additional time, complexity, and cost to the development of their applications.

A blockchain node for an application-focused Cosmos blockchain consists of a state-machine, built with the Cosmos SDK, and the consensus and networking layer, which are handled by CometBFT (opens new window).

CometBFT is a high-performance, consistent, flexible, and secure consensus module with strict fork accountability. It relies on Proof-of-Stake (PoS) with delegation and Practical Byzantine Fault Tolerance (opens new window). Participants signal support for well-behaved, reliable nodes that create and confirm blocks. Users signal support by staking ATOM, or the native token of the respective chain. Staking bears the possibility of acquiring a share of the network transaction fees, but also the risk of reduced returns or even losses should the supported node become unreliable.

Application Blockchain Interface (ABCI)

By Satya Nayak

CometBFT (opens new window)packages the networking and consensus layers of a blockchain and presents an interface to the application layer, the Application Blockchain Interface (ABCI). Developers can focus on higher-order concerns and delegate peer-discovery, validator selection, staking, upgrades, and consensus to CometBFT. The consensus engine runs in one process and controls the state machine, while the application runs in another process. The architecture is equally appropriate for private or public blockchains.

CometBFT is connected to the application by a socket protocol. ABCI provides a socket for applications written in other languages. If the application is written in the same language as the CometBFT implementation, the socket is not used.

CometBFT provides security guarantees, including the following:

Forks are never created, provided that at least half the validators are honest. Strict accountability for fork creation allows determination of liability. Transactions are finalized as soon as a block is created. CometBFT is not concerned with the interpretation of transactions. That occurs at the application layer. CometBFT presents confirmed, well-formed transactions and blocks of transactions agnostically. CometBFT is un-opinionated about the meaning any transactions have.

The block time is approximately seven seconds, and blocks may contain thousands of transactions. Transactions are finalized and cannot be overturned as soon as they appear in a block.