The security of cross-chain interoperability depends on its weakest (or most trusted) link, and the security model of trust-based cross-chain protocols takes into account the additional security assumptions of third parties.
Last night, Axie Infinity’s exclusive sidechain Ronin was revealed to have stolen $624 million worth of encrypted assets (including 173,600 ETH and 25.5 million USDC), which is also the most costly cross-chain bridge security incident to date.
Embarrassingly, this hack happened 6 days ago.
So how exactly was Ronin stolen? As an Ethereum side chain, Ronin’s cross-chain bridge uses MPC threshold signature technology. Among the 9 validator keys set by it, 5 or more validator keys are required to approve deposits and withdrawals. trade.
And 4 of them are managed by the same person (i.e. Sky Mavis), which means that as long as the attacker controls the key of Sky Mavis and then another validator key, then the entire Ronin network is The funds are in the hands of hackers.
At present, most cross-chain bridge projects use such multi-signature technology. Therefore, in theory, these projects may also suffer from similar attacks.
Cross-chain attacks that have already appeared
The private key attack is just one of the ways to attack the cross-chain bridge.
For example, in the previous Poly Network ( O3 and other projects) hacking incident, the hacker did not complete the attack by stealing the private key, but implemented the attack through the contract permission vulnerability.
Another example is the Wormhole cross-chain bridge that happened some time ago. The attacker also took advantage of the contract loophole of the cross-chain bridge, deceived the signatures of the multi-signers, minted 120,000 Wormhole ETH, and finally transferred the locked 80,000 ETH to the attacker. Your own wallet (Note: For detailed attack methods, see “Solana Cross-Chain Bridge Project Wormhole was hacked and lost nearly $300 million” compiled by DeFi Way).
In addition, there have been cross-chain attacks such as counterfeit currency recharge and fake websites in history, which basically revolve around private key and contract loopholes.
Security implications of LayerZero (stargate)
Next, let’s talk about the recently popular cross-chain project LayerZero, and the first cross-chain application stargate based on this protocol.
As of press time, there are already $3.38 billion worth of stablecoins in stargate’s pool.
However, the security risks of this cross-chain project are also worrying.
For example, last week it was warned by the Optimism team that someone was trying to conduct an unusual attack on Stargate, and the stargate team turned to white hat hackers such as samczsun for help, and later fixed the critical vulnerability. And Stargate’s problems don’t stop there. A few days ago, it was revealed that Stargate’s core contracts are controlled by an EOA address private key, which means that if the private key is leaked, or the project party wants to do evil, the consequences will be unimaginable. .
At present, although Stargate has changed to a 2/3 multi-signature mechanism, it may still encounter the risk of a managed key attack like Ronin Network.
(Note: This article does not mean that the cross-chain model of repeaters and oracles adopted by Stargate has no value, but that the underlying infrastructure is still the same as some other cross-chain bridge projects)
There are so many security problems in the cross-chain bridge, is there really no hope?
Trust-minimized cross-chain bridge
Not so absolute, just saying that we are still in the early stage of cross-chain, and by adopting a trustless approach, we can reduce some potential attack surfaces, thereby improving the security of the system
Nomad relying on fraud proofs
For example, Nomad employs an optimistic mechanism to improve the security of cross-chain communication, which avoids the use of new cryptography and relies on fraud proofs and issuance proofs to prevent channel failures.
The core design of the protocol is revocation (revocation) rather than permission (authorization), which means that the key manager can only revoke access, but not allow access. In other words, even if the attacker controls all the management keys of the system, He also can’t steal funds, and the worst thing he can do is DoS the entire network.
Note: Nomad may still have the risk of contract vulnerabilities.
IBC with light client, Near rainbow bridge, etc.
Over the years, the cross-chain communication protocol using light client & relay has proved to be the most secure cross-chain method at present. For example, the IBC communication protocol of the Cosmos ecosystem, its security comes from the finality of the Tendermint consensus, and its design does not require the introduction of A trusted third party, a handshake (mimicking a TCP/IP handshake) is first initiated between the two chains that want to connect, and then confirmed. To confirm transactions, the validity rules of one chain are encoded directly into the IBC light client on the other chain, and state verification is performed against these rules.
The light client can then verify the state of the chain on the other end of the ibc transaction by validating the Merkle proof of the block header associated with the transaction against the latest consistent state of the counterparty chain.
This stateful verification technology, along with a live network of repeater operators passing packets back and forth, ensures that IBC remains highly secure and permissionless.
However, the light client approach means that IBC can only be limited to its ecosystem at present, and cannot effectively expand to EVM ecosystems such as Ethereum.
In addition, cross-chaining through IBC is not absolutely safe. As Vitalik mentioned in a post written 2 months ago, when there are more blockchains connected by the cross-chain protocol, the problem will be The worse it gets, if there are 100 blockchains connected to each other through IBC, then there will be many interdependent dapps between these chains, and 51% attacking one of the chains will also cause systemic infection, thus threatening the entire ecosystem system economy.
To recall the sentence at the beginning of the article: the security of cross-chain interoperability depends on its weakest (or most trusted) link. This actually means that it is difficult for the Cosmos ecosystem to achieve more long-tail chain expansion without addressing shared security, which is also the focus of Cosmos this year.
Of course, Vitalik also mentioned that these problems will not appear immediately. 51% attack on any PoS chain will cost a lot, but his reminder is indeed worthy of our attention.
Trust-minimized rollup cross-chain bridge
Let’s briefly talk about the rollup cross-chain bridge that is currently most relied on by the Ethereum ecosystem. Compared with the side-chain cross-chain bridge, the current rollup cross-chain bridge may not seem to be fundamentally different. Both will rely on n-of-m. Federal trust model (that is, multi-signature), but the rollup cross-chain bridge can remove this trust model with the development, and the ultimate risk lies in the smart contract itself, and the cross-chain bridge of the side chain can only rely on this federal trust trust. model, but also face smart contract risk and 51% attack risk.
some simple advice
The cross-chain water is too deep, and almost every solution will face a variety of potential attack methods. The more complex the system design, the greater the possibility of encountering attacks. Therefore, the author does not recommend using existing cross-chain solutions. Chain bridges transfer excessive assets between various public chains. If there is a real need, then I would suggest the following ways to reduce the risk of being attacked;
- Through a safer centralized exchange, the native assets of the corresponding chain are exchanged, and then extracted to the corresponding chain to avoid possible smart contract risks.
- Adopt trust-minimized cross-chain bridges, such as IBC, Nomad, and mature rollup cross-chain bridges.
- Regardless of the TVL indicator for the time being, the higher the value, the greater the possibility of the cross-chain bridge being hacked.
- Adopt cross-chain bridges that have existed for a long time and have never had a safety accident, and try to avoid using cross-chain bridges between different ecosystems.
Finally, I sincerely hope that the cross-chain bridge will become more and more secure.
Posted by:CoinYuppie，Reprinted with attribution to:https://coinyuppie.com/can-i-still-use-cross-chain-bridge-safety-accidents-frequently/
Coinyuppie is an open information publishing platform, all information provided is not related to the views and positions of coinyuppie, and does not constitute any investment and financial advice. Users are expected to carefully screen and prevent risks.