# Casper the Friendly Finality Gadget

arXiv: https://arxiv.org/abs/1710.09437 · HTML: https://mlsanity.com/paper/1710.09437/

## Key facts

- Cited by 5 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 25 Oct 2017.

## Built on by (most cited first, 5 of 5)

- [Implicit Model Specialization through DAG-based Decentralized Federated Learning](https://mlsanity.com/paper/2111.01257/) (2021)
- [Social Choice Around the Block: On the Computational Social Choice of Blockchain](https://mlsanity.com/paper/2203.07777/) (2022)
- [Securing Health Data on the Blockchain: A Differential Privacy and Federated Learning Framework](https://mlsanity.com/paper/2405.11580/) (2024)
- [OVIG: Optimistic Verification of AI Training Integrity via Gradient Signals](https://mlsanity.com/paper/2606.21045/) (2026)
- [Byzantine Accountability Without Consensus: Strong Eventual Consistency for Non-Associative, Stochastic, Robust Aggregation](https://mlsanity.com/paper/2607.10305/) (2026)

## Abstract (arXiv)

We introduce Casper, a proof of stake-based finality system which overlays an existing proof of work blockchain. Casper is a partial consensus mechanism combining proof of stake algorithm research and Byzantine fault tolerant consensus theory. We introduce our system, prove some desirable features, and show defenses against long range revisions and catastrophic crashes. The Casper overlay provides almost any proof of work chain with additional protections against block reversions.