On a Reddit post on Friday Vitalik Buterin, the co-founder of Ethereum (ETH) outlined critical security concerns related to cross-chain bridges in the blockchain ecosystem. As Buterin says, storing native assets right on the chain (Ethereum on Ethereum, Solana on Solana, etc.) offers some level of immunity to 51% attacks. Even if hackers manage to censor or reverse transactions, they cannot propose blocks to steal their own crypto.
The rule also applies to the Ethereum application. For example, if hackers launch a 51% attack (by controlling 51% of the total circulating ETH supply) while an investor exchanges 100 ETH for 320,000 DAI stablecoin, the final state will remain unchanged. That means the investor would always get either 100 ETH or 320,000 DAI.
However, Buterin went on to say that the same level of security does not apply to cross-chain bridges. In the example he mentioned, when an attacker sets up his own ETH on a Solana (SOL) Bridge to get Solana-wrapped Ether (WETH), and to reverse this transaction on the Ethereum side, once the Solana side confirmed it, it would cause devastating losses for other users whose tokens are in SOL-WETH -Contract are blocked because the packaged tokens are no longer supported by the original in a 1: 1 ratio.
Buterin further outlined how the security exploit could scale negatively as more bridges are added to a cross-chain network. In a theoretical network with 100 chains, the high interdependence and overlapping derivatives would mean that a 51% attack on a chain, especially a small-cap chain, can cause system-wide contagion. To for Crypto 51, it costs hackers up to 1.78 million US dollars per hour to set up a 51% attack vector against the Ethereum network. For blockchains like Bitcoin Cash, however, the cost drops to just $ 13,846 per hour.
My argument for why the future will be * multi-chain * but not * cross-chain *: There are fundamental limits to the safety of bridges that hop across multiple “zones of sovereignty”. from https://t.co/3g1GUvuA3A: pic.twitter.com/tEYz8vb59b
– vitalik.eth (@VitalikButerin) January 7, 2022
Related: Vitalik proposes new “multidimensional” Ethereum fee structure
