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Reduction components

This package defines the components for both the first and second step of reduction individually, as specified in the Binary Reduction Phase of the SBA* consensus protocol.

Due to small, but intricate differences between the two steps, the components are defined individually, with a minimal amount of shared code. This was done in an effort to increase readability, since it avoids massive amounts of abstraction which, on earlier iterations of the package, caused some confusion for readers. That said, code which is identical across the two components is defined in the top-level of the package, and imported down.

Values

Block Reduction Event

Field Type
signedblockhash BLS Signature

Architecture

At the core, a Reducer works like this:

  • It gets triggered by a call to the Run function. This instantiates an Aggregator, starts a timer, and gossips a Reduction message (using the provided keys on startup)
  • The queue is flushed, and it starts collecting Reduction messages, passing them down to the Aggregator
  • When the Aggregator reaches quorum, or when the timer is triggered, the Reducer will return a message
  • The component is then finished and waits for the next call to Run

Differences between the two components

Since there are subtle differences in the actions that need to be taken per step, the reducers have been split up in a first step and second step. Between the two, these differences can be found:

  • Upon reaching quorum, the first step reducer will attempt to retrieve the candidate block corresponding to the winning hash (either through the DB or the network), and attempt to verify it, to make sure it's okay to continue voting on this block for the second step
  • When reaching quorum, the first step reducer will return a StepVotes message, which is passed on to the second step reducer. The second step reducer will instead gossip an Agreement message, using the combined StepVotes of the first and second step to create a certificate. The second step reducer does not return anything

Aggregator

Each Reducer makes use of an Aggregator, which is a component akin to a storage for incoming messages. The Aggregator will receive any incoming Reduction messages after they are filtered by the Reducer. It will separate messages by their block hash, and proceed to aggregate the included signedblockhash with other collected signatures for this hash (if any). Additionally, it saves the senders BLS public key in a sortedset.Set. Once the amount of keys and signatures for a certain blockhash exceeds a threshold, the Aggregator will return the collected information.