Long range attack

Written by Eric Choy

Introduction

A Long Range Attack is a theoretical threat to undermine Proof of Stake consensus blockchains. Similar to the 51% attack on Proof of Work consensus blockchains, Long Range Attack is a way for an adversary to take over a blockchain with a false chain. Essentially how this works is that an adversary can start with the Genesis block of the blockchain, including having a significant stake of the token balance higher than the forging balance, and then start to deceive nodes by creating their own branch of the chain, indistinguishable from the real chain. This is avail to adversaries due to Weak Subjectivity and Costless Simulation.

Long Range Attacks can comprise of three different methods:

1. Simple

2. Posterior Corruption

3. Stake Bleeding

Although Long Range Attacks have never been performed on a blockchain, there are mechanisms to prevent such an attack from happening such as assigning a list of bootstrap nodes, implementing checkpoints, and assigning a range of blocks to always be considered true.

Suggested Reading

Rewriting History: A Brief Introduction to Long Range Attacks by Evangelos Deirmentzoglou

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