https://github.com/timyiu478/ben-or-consensus
A Ben-Or’s protocol for Binary Asynchronous Agreement
https://github.com/timyiu478/ben-or-consensus
asychronous-network ben-or consensus-algorithm fault-tolerance random
Last synced: 7 months ago
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A Ben-Or’s protocol for Binary Asynchronous Agreement
- Host: GitHub
- URL: https://github.com/timyiu478/ben-or-consensus
- Owner: timyiu478
- License: mit
- Created: 2025-09-23T14:16:12.000Z (9 months ago)
- Default Branch: main
- Last Pushed: 2025-10-15T04:50:52.000Z (8 months ago)
- Last Synced: 2025-10-15T15:49:07.434Z (8 months ago)
- Topics: asychronous-network, ben-or, consensus-algorithm, fault-tolerance, random
- Language: TypeScript
- Homepage:
- Size: 20.4 MB
- Stars: 0
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
## The Ben-Or decentralized consensus algorithm
The *Ben-Or consensus algorithm* is making use of **randomness** to create consensus in a asynchronous network with eventual liveness guarantee.
This repository contains my TypeScript implementation of the Ben-Or consensus algorithm, designed to run on a single machine. It's for anyone looking to learn more about this algorithm from a hands-on perspective.
---
## Example Run
Example Configuration:
```
?: no init value
H: Non-Faulty
F: Faulty
Nodes: F F F F H H H H H H
Init Values: 1 1 1 1 ? 1 0 1 0 1
```
Run:
See [start.ts](src/start.ts) for the details
---
## How to test the code
1. Run the unit tests with the command `yarn test` and see how the implementation performs against the given tests
1. Modify the `start.ts` file with the parameters you'd like, launch the network manually with `yarn start` and see the results
---
## Algorithm Details
### Intuition of the algorithm
1. At first every process proposes their input value.
1. After that, they propose random values.
1. **When enough processes propose the same value, the value is chosen.**
1. Eventually, that will happen!
### Setup
1. Protocol proceeds in **asynchronous rounds**, where each round has **two** phases.
1. In the first phase of a round, each node tries to identify a value supported by a majority in order to propose that for the second phase.
1. In the second phase (the decision phase), a node finalizes its decision if it finds the same value proposed by at least *f+1* nodes.
1. For each phase, processes broadcast their input values and wait for *n - f* messages from the other processes.
1. Each message is tagged with the round and phase number. (And messages can be resent to deal with a lossy network. But once a message is sent, that value is **locked** in for that process for that phase/round.)
### Guarantees
1. Deterministic Safety by majority intersection
1. Termination with probability 1
### Pros and Cons
Pros:
1. Processes without input values start by proposing *⊥*
Cons:
1. Performance is not predictable.
1. Convergence can still take multiple rounds.
1. Amount of communication needed is potentially high.
### Assumptions
1. Node Failure Mode: crash-stop start from round 0
1. Message sent will eventually be received in arbitrary order; No message lost
### REST API
- Nodes listen to request on the port defined by `BASE_NODE_PORT` + nodeId, which for the basic configuration, means that node #0 will have the port 3000, #1 the port 3001, etc,
- Nodes always start with an initial state that is provided as a parameter of the `node` function,
- Nodes communicate through POST HTTP request with the `/message` route which you should implement,
- Nodes should start the algorithm when they receive a GET HTTP request to the `/start` route,
- if the `/stop` GET HTTP route is called on a node, it should stop any activity (this is to prevent any errors in the tests),
---
## References
1. Asynchronous Agreement Part Two: Ben-Or's protocol - https://decentralizedthoughts.github.io/2022-03-30-asynchronous-agreement-part-two-ben-ors-protocol/
1. Lecture CSE2 G20 Randomized consensus - https://courses.cs.washington.edu/courses/cse452/19sp/slides/l13-benor.pdf