Dave: Not the hero we want, but the hero we need

Safety has always been a keyword in the crypto space. Without complex systems, algorithms, and processes to fiercely resist attacks, this industry could not have grown into a behemoth with a market cap exceeding $3 trillion in under twenty years. As you stroll along the first line of defense, you inevitably encounter anti-fraud systems that prevent invalid state transitions by allowing anyone to challenge and prove dishonest behavior. In the case of Layer-2 rollups, they package thousands of off-chain transactions into a single on-chain record, with anti-fraud proofs essentially acting as a 'guard force'.

Since Layer-2 rollups regularly submit states to the mainnet, these states are either formally recognized through anti-fraud proofs or are optimistically assumed to be valid (which can later be challenged and proven with anti-fraud proofs), such algorithms must be very robust. Especially now, with over $30 billion in value locked in. However, the vulnerabilities in anti-fraud proofs make them a ticking time bomb in the L2 ecosystem.

Thus, Cartesi designed a new permissionless, interactive anti-fraud system called Dave. While its name may sound like an unremarkable ordinary person standing at a bar, Dave might actually be the answer to securing the $30 billion total locked value (TVL).

Optimistic Rollups: Scaling Ethereum, but at what cost?

Let’s delve into Optimistic Rollups (ORs), the darlings of the Ethereum scaling ecosystem. They are named so because they pre-assume off-chain transactions are valid (without prior anti-fraud proofs), and these L2 protocols pride themselves on increasing Ethereum's throughput by up to 100 times.

By binding security to Ethereum's base layer, ORs publish transaction results on-chain while processing batch transactions off-chain. Naturally, there must be a backing to ensure everyone's honesty, which exists in the form of a challenge system—where batch transactions can be questioned with anti-fraud proofs within a specified timeframe. This way, security is maintained without continuous on-chain verification.

But the problem is: traditional anti-fraud algorithms have flaws. In fact, there are quite a few defects. Participating in dispute resolution is not only costly but also susceptible to 'Sybil attacks'—where an attacker floods the system with fake identities—which can overwhelm these mechanisms. Moreover, the entire process is extremely lengthy, meaning a well-funded adversary can potentially win after a prolonged war of resource attrition. A successful Sybil attack is akin to evil forces on the battlefield overwhelming noble but outnumbered heroes.

Cartesi's Anti-Fraud Game Changer

The think tank of the modular blockchain protocol Cartesi could not sit idly by and ignore the potentially fatal flaws of Optimism's OPFP and Arbitrum's BoLD. Instead, their ingenuity developed Dave, designed to serve as a 'public good' for the Ethereum ecosystem. Dave is based on Cartesi's Permissionless Refereed Tournaments (PRT) primitives, balancing decentralization, security, and liveness, creating a robust line of defense against malicious actors, virtually unaffected by Sybil attacks, as even a single honest validator can enforce the correct state on-chain—regardless of how many adversaries initiate an attack.

What’s the secret of Dave? A divide-and-conquer strategy that forces Sybil attackers to fight among themselves, leading to their self-destruction while honest validators face minimal resistance. The design of the algorithm results in exponential increases in delay and resource costs for attackers launching Sybil attacks, while the cost for honest participants remains negligible. A recent post at https://t.co/VvTpEVZfju demonstrates how Dave can thwart a million ETH Sybil attack with just 7 ETH from honest validators.

Another clever feature of the system is the speed of dispute resolution; for any realistic number of Sybil attacks, disputes can be resolved within 2-5 challenge cycles, keeping the network running smoothly.

Unlike OPFP or BoLD, Dave allows (but does not require) honest validators to collaborate trustlessly as a collective action without centralized trust. Because you don’t have to be a crypto whale to fight fraud, it empowers smaller players to protect the integrity of rollups, no matter who the adversary is. In short, the attempts of fraudsters to manipulate ORs are destined to fail: the mathematical principles behind Dave make manipulation a losing gamble.

The moment of truth arrives, and Dave steps up

Rollups are not a trivial branch of the crypto world; they have now become its pillars. As more value accumulates on L2 and ORs, traditional anti-fraud proofs need to be redesigned, just as a powerful army must embrace new technologies and rejuvenate itself through new blood for future strength.

Dave may be the optimal solution, providing resistance to Sybil attacks, fast dispute resolution, and minimal resource demands on honest validators. Cartesi focuses on application-specific rollups, making Dave a natural choice to scale Ethereum's security while keeping L2 lean and efficient.