Polygon co-founder Sandeep: Writing after the chain bridge chain explosion

Author: Sandeep

Compiled by: Jiahua, ChainCatcher

This weekend has been heart-wrenching. Three cross-chain bridge security incidents occurred within three weeks. I haven't been focused on the specifics of any one attack these days, but rather on the patterns hidden behind all these events.

On April 1, Drift lost $285 million.

On April 13, Polkadot Hyperbridge minted 1 billion unsupported tokens through a replay proof; had it not been for the already thin liquidity on the target chain, the losses would have been much greater.

On April 18, KelpDAO lost $292 million. Prior to this, there were also Wormhole, Ronin, Harmony, BNB Bridge, Nomad, and Multichain.

First and foremost, I want to express my utmost respect for every team that actively responded during this stressful weekend. I have no intention of kicking anyone while they are handling emergencies.

We have all been in similar situations, and the teams currently releasing patches are working very hard. Kelp's emergency pause multi-signature mechanism prevented two subsequent asset drain attempts; otherwise, the losses would have increased by another $200 million.

What I want to emphasize here is that what happened this weekend is not just a Kelp issue. It stems from a design choice that the entire industry has been making. Currently, most cross-chain infrastructure in cryptocurrency still functions like a notary.

Whether you call it DVN, a relay set, an oracle committee, or multi-signature, the essence is that a small committee monitors activities on one chain and certifies them on another chain.

Once this committee or its underlying price feed data is compromised, this notary will unreservedly endorse lies. The names of the protocols may change, but the trust assumptions have never changed.

@moo9000 aptly named it: MultisigFi.

This description is spot on. No matter what you call the underlying committee, the trust model is the same, and the events of the past three weeks painfully highlight how this model collapses when scaled.

A recent Dune data scan of active LayerZero applications found that 47% of applications run on a 1/1 validator configuration, 45% run on a 2/2 configuration, and less than 5% of applications have adopted more robust security configurations.

This means that for 90% of the cross-chain applications currently in production, 1 to 2 compromised signers are the only security barrier between user funds and attackers.

Five years ago, this might have been a defensible default security setting. At that time, cross-chain bridges only transferred millions of dollars, and no one was probing them at an industrial scale.

But this is nonsensical in 2026. The same design is now transferring billions of dollars! Moreover, AI-assisted tools are continuously discovering operational configuration vulnerabilities at machine speed. The attack surface has expanded exponentially, while the security model remains stagnant.

To be clear, this is not an article that pits Polygon against everyone else. Years ago, we also built an early version of this trust assumption into our products. We learned from it, and the entire industry has learned from it.

Along the way, some of us continued to build under the committee model, while others have bet the entire company on ZK (zero-knowledge proofs).

Our bet on ZK is not just talk: in July 2024, we launched ZK proofs for the Agglayer bridge, which has been in production for over a year, settling cross-chain transactions at scale every day. Frankly, what happened this weekend only further solidified my confidence in this argument.

ZK proofs take over the work previously done by committees. They act like a tiny cryptographic receipt, proving that a computation was indeed executed correctly, and any machine on Earth can verify it in a matter of milliseconds.

Either the proof holds, and the transfer settles, or the mathematical verification fails, and the assets remain untouched. No operator can be bribed, no RPC can be poisoned, no quorum needs to be coordinated, and no one will be sitting in a room at 3 AM on a Saturday deciding whether your money is safe.

On top of that is what we call "Pessimistic Proof." The simplest way to understand it is: do not trust anyone's on-chain accounting.

Every chain connected to Agglayer has a dynamic ledger recording the receipt and dispatch of assets, and the accounts must remain balanced before any withdrawal is finally confirmed. A chain can never withdraw more of an asset than what is recorded, regardless of the reason or whether someone has forged upstream messages.

Mathematical rules will not allow such things to happen. Agglayer enforces this through the Succinct SP1 proof system, built on Polygon Plonky3.

If last weekend's scenario were run on Agglayer, the pessimistic proof would have immediately blocked withdrawals because there were no deposit records, so funds would absolutely not transfer.

The same accounting mechanism could capture the infinite minting vulnerabilities of Wormhole, BNB Bridge, and the replay proof vulnerability of Hyperbridge.

These vulnerabilities are fundamentally different, but they all boil down to the same issue: cross-chain bridges released assets that had no support on the other end. Agglayer would prevent all of these situations before any settlement occurs.

This is not just theoretical. While a significant portion of DeFi hit the pause button this weekend, Agglayer processed about $200 million in bridging transaction volume, completely unscathed.

Katana, natively connected to Agglayer, maintained zero risk exposure throughout the entire event. Before the root cause was publicly disclosed, our security team paused the LayerZero integrations across the entire Polygon ecosystem, and our product and support teams were on the phone with institutional partners throughout the weekend.

Nearly six years of building. $24 trillion settled on Polygon. 7 billion transactions. 99.99% uptime. Zero cross-chain bridge vulnerabilities on Agglayer. This is why we spent years building Agglayer; security has always been our top priority.

I present these numbers not to boast, but because to walk confidently into an institution and tell them that cryptocurrency is ready to handle massive payment volumes, you must present these tangible achievements.

Building cross-chain bridges based on committees is cheaper and faster; I understand why teams would build them, and we have also built early versions. However, what attackers can do has indeed changed.

Since 2022, the Lazarus group has been attacking these designs, and they show no signs of slowing down. AI-assisted audits can now uncover all the configuration errors that were previously hidden under complex hierarchies. These attacks will not disappear. Mathematics will eventually catch up with the shortcomings of committees.

For the past two to three years, this industry has been settling trillions of dollars in transaction volume annually. We are asking banks and payment companies to place huge sums of money on tracks that still rely on one or two signers making the right judgment on a Saturday night. This is our demand; saying it out loud makes you realize how absurd it is.

We must do better, and we already know how to do it.

That said, it is important to acknowledge that LayerZero is now disabling 1/1 settings (single-signature) across the industry. This is the right decision, and it will make cross-chain security much stronger; I fully support it. Other teams will also continue to strengthen their committee designs. This work is important.

But the bigger shift is in the architecture. ZK proofs are tireless, immune to social engineering attacks, and will not have a bad weekend. Mathematics either holds or it doesn't; if it doesn't, nothing will settle.

This is the direction the industry is moving in, and the pace is faster now than it was a month ago, which is good news for every builder and every institution entering the chain.

This week, every team building cross-chain infrastructure should ask themselves one question: do I really need a committee? Strengthening existing committees is merely a fallback approach.

Agglayer is open source. No protocol fees. No permission restrictions. Any team ready to transition from trusted proof mechanisms to cryptographic verification can connect. If you are currently running a cross-chain bridge and the events of the past three weeks have made you rethink your trust model, please contact us.

This is not a competitive moat we are hoarding; it is infrastructure that the entire industry should be using.

The fate of cryptocurrency over the next decade will be determined by those teams willing to tackle more hardcore architectures now. Cryptographic proofs are harder to establish than notaries. But they will not collapse over the weekend, and they can scale to the trillions that cryptocurrency is already being asked to handle.

Do you want a committee or a mathematical proof? We chose the latter. I hope more people choose the same.

After this weekend, I am more convinced of ZK cross-chain. In tough times, forge clear architecture.