Implement Tendermint-Style BFT Voting Rounds - The Consensus

                      TASK
                    

Implementation

Research and implement Tendermint-style BFT voting (used in Cosmos blockchain). Tendermint simplifies PBFT with clear round structure and a rotating proposer.

Round structure:

Propose: Round proposer broadcasts a block
Prevote: Each validator broadcasts prevote (for the block or nil)
Precommit: If 2/3+ prevotes for a block, broadcast precommit. If 2/3+ precommits, commit.

Request:  {"type": "tendermint_propose", "msg_id": 1, "round": 0, "proposer": "v1", "block": {"height": 1, "txs": ["tx1", "tx2"]}}
Response: {"type": "tendermint_propose_ok", "in_reply_to": 1, "round": 0, "block_hash": "abc123"}

Request:  {"type": "tendermint_prevote", "msg_id": 2, "round": 0, "validator": "v2", "block_hash": "abc123"}
Response: {"type": "tendermint_prevote_ok", "in_reply_to": 2, "prevotes_for_block": 2, "total_prevotes": 3, "threshold": 3}

Request:  {"type": "tendermint_status", "msg_id": 3, "round": 0}
Response: {"type": "tendermint_status_ok", "in_reply_to": 3, "phase": "precommit", "block_committed": false, "prevote_count": 3, "precommit_count": 2}

Sample Test Cases

Proposer broadcasts blockTimeout: 5000ms

Input

{"src":"c0","dest":"n1","body":{"type":"init","msg_id":1,"node_id":"n1","node_ids":["n1","n2","n3","n4"]}}
{"src":"c1","dest":"n1","body":{"type":"tendermint_propose","msg_id":2,"round":0,"proposer":"n1","block":{"height":1,"txs":["tx1"]}}}

Expected Output

{"src": "n1", "dest": "c0", "body": {"type": "init_ok", "in_reply_to": 1, "msg_id": 0}}

Prevotes accumulate toward thresholdTimeout: 5000ms

Input

{"src":"c0","dest":"n1","body":{"type":"init","msg_id":1,"node_id":"n1","node_ids":["n1","n2","n3","n4"]}}
{"src":"c1","dest":"n1","body":{"type":"tendermint_propose","msg_id":2,"round":0,"proposer":"n1","block":{"height":1,"txs":["tx1"]}}}
{"src":"c1","dest":"n1","body":{"type":"tendermint_prevote","msg_id":3,"round":0,"validator":"n2","block_hash":"abc"}}

Expected Output

{"src": "n1", "dest": "c0", "body": {"type": "init_ok", "in_reply_to": 1, "msg_id": 0}}

Hints

Hint 1▾

Tendermint simplifies PBFT by using rounds with a rotating proposer

Hint 2▾

Each round has: Propose, Prevote, Precommit phases

Hint 3▾

A block is committed when 2/3+ of validators precommit for it

Hint 4▾

Validators lock on a value after precommitting (prevents equivocation across rounds)

Hint 5▾

The lock is released only if a higher round proposes a different value with enough prevotes

Resources

Tendermint: Byzantine Fault Tolerance in the Age of Blockchains

Tendermint BFT consensus used in Cosmos blockchain

                      OVERVIEW
                    

Theoretical Hub

Concept overview coming soon

Key Concepts

TendermintCosmosblockchainvoting roundslock mechanism

main.py

python