Segregated Byzantine Agreement (SBA) is a privacy-orientated consensus mechanism. It departs from consensus mechanisms like PoW/PoS, which are poorly suited for privacy.
SBA uses existing ideas like Cryptograpic Sortition (lottery) and combines it with concepts like stealth time-locked transactions to implement simple but secure communication that can be audited. SBA makes use of a few different types of actors in the network to reach consensus.
- 1. (super)Nodes. These are points in the network that facilitate transactions. They compete with each other for the generating and proposing blocks. These are computationally very light tasks, and a node will not require high computational power, or a big stake.
- 2. Provisioners. These are nodes that have committed a certain minimum stake to the network and take care of more intensive tasks such as block verification, voting, and notarization (VVN operations). These types of nodes are non-transactional.
SBA foresees different subsequent cyclic phases:
- 1. Block Generation Sortition — nodes participate in sortition(lottery) to acquire the right to broadcast a block proposal.
- 2. Default Block Generation Sortition — run by Provisioners in parallel to the Block Generation Sortition. They will propose a default empty block, in case consensus is not reached on the proposed block.
- 3. Validation — run by a subset of Provisioners called Verifiers. Verifiers confirm the legitimacy of the block proposal and its proposing candidate. If everything was done correctly they will sign the proposed block, otherwise they will sign the default block proposed by the provisioners.
- 4. Voting — a number of rounds each of which run by a different subset of Provisioners called Voters. Once consensus is reached on the block it can be notarised and added to the chain. If consensus is not reached they will vote to add an empty block.
- 5. Notarisation — the Voters which reached voting consensus on the pre-block are called Notaries. Their public key is added to the pre-block and they play the role of Verifiers in the next block’s Validation phase. The pre-block is then turned into an official block by the Notaries.
SortitionA node that wishes to participate in the sortition (and become a Block Generation candidate)is first required to lock an arbitrary amount of tokens.
RewardsIn addition to finalizing a block onto the chain, Notaries are also responsible for a secondary procedure which generates the block rewards through a set of coin-base transactions, essentially minting new tokens. The block rewards, together with the provisioner’s ROI, will form the network’s inflation rate.
