ISS-Based BFT #53 Milestone 2: Parallel Ordering & BFT Timestamping

Milestone 2: Parallel Ordering & BFT Timestamping

| Estimated Delivery | Month 3 (June 2026 if approved in March) | | :---- | :---- | | Focus | ISS-based parallel consensus with deterministic timestamp assignment |

Deliverables:

• ISS ordering module: epoch-based log subdivision with configurable epoch length (k slots) and segment count (s segments).
• Parallel consensus across segments, with each validator leading sequential instances within its assigned segment.
• Output module: deterministic transformation of ordered blocks, replacing batch references with full request data.
• Median-based BFT timestamp assignment using 2f+1 canonical signed protocol messages per validator block.
• Post-order timestamp shifting to maintain globally strictly increasing timestamps across interleaved parallel output.
• Per-transaction timestamp assignment at microsecond granularity with configurable block time granularity.
• Handling of edge cases: genesis/bootstrap blocks, end-of-epoch timestamp derivation, cancelled blocks (⊥ values).
• Integration test demonstrating parallel ordering across 4+ validators with consistent timestamp assignment and zero data loss.

Acceptance Criteria: Verification of parallel consensus processing

_Originally posted by @hythloda in https://github.com/canton-foundation/canton-dev-fund/issues/53#issuecomment-4254772763_