How does Pulsar achieve succinct BFT?

Pulsar brings both technologies, succinctness and BFT, in order to solve the very well known trilemma of blockchain.

The magic trick is using both consensus mechanisms at the same time: Pulsar’s validator set uses a very fast consensus engine, CometBFT, allowing single-block finality and high TPS. In addition, all actions on Pulsar are settled on the second consensus regularly in the form of a zk-SNARK, making the information on Pulsar succinct after a certain number of blocks. However, this number of blocks is also bounded (about 32), thus the overall Pulsar design is always succinct. Essentially, verification of Pulsar becomes the verification of the most recent succinct block, and then the synchronization of the last 32 blocks, which is also a constant-sized process.

For CometBFT, Pulsar powers up a CosmosSDK chain, which is easily customizable for the needs of Pulsar. For the succinct settlement, Pulsar uses Mina’s proof system and blockchain, making sure that each block is made succinct with a bounded delay.

Since we use the word settlement, Pulsar can easily be confused with a ZK rollup, which is not an accurate description. In rollups, the security is fully brought from the settlement layer. In Pulsar’s design, the settlement layer, Mina, is only responsible for the succinct proofs of Pulsar. Pulsar has its own consensus and economical security with a validator set, making it also resistant to censorship and achieve full-security single-block execution. In rollups, no TX can be considered secure before the batch including the TX is settled and verified on the settlement chain. This is not like that in Pulsar: Every TX is final and succinctly provable once the CometBFT consensus is finalized, which takes a single block (about a few seconds).

Moreover, since Pulsar is always eventually settled on Mina, each block is succinct at the moment of finality. An important observation here is that the settlement of Pulsar on Mina does not make the block succinct, at least not yet. Pulsar’s succinctness should also wait for Mina’s finality. However, this waiting is bounded, and the number of blocks that has passed from the latest succinct check point is always a constant. This important observation allows Pulsar to keep its succinctness property without being affected by Mina’s consensus choice.

This unique design of Pulsar is essentially a mesh security set up: Pulsar’s power comes from zero-knowledge proofs, CometBFT, and Ouroborus, all at the same time. This allows Pulsar to solve the trilemma without sacrificing anything.

Yet, using so many technologies together has its own difficulties, and Pulsar solves all of them with three vital components:

• AtomOne ICS Restake Chains
• IBC Bridging Layer
• The Succinct Prover Node and Mina Bridge Node

Let’s see each one in its full capacity!