Bridges

Why so weak?

• Many people think that after a 51% attack (where a hacker takes over more than 50% of a blockchain network), the entire network breaks. Vitalik disagrees with this.
• He says that if Ethereum succumbs to a 51% attack and you have 100 ETH in your wallet, the hacker cannot propose a block that takes away your 100 ETH, because it goes against protocol rules.
• However, in the case of a bridge - the two networks on either side of a bridge will have different rules and standards.
• So if there is a bridge between Ethereum and Network X, the Ethereum network has no way of verifying transactions that took place on the Network X side of the bridge.
• If I can hack Network X and I then tell the Ethereum side of the bridge that I now have $100 million in my wallet, the Ethereum side will accept this and allow me to cash out.
• In this way, I can hack one side of a bridge and cash out on the other side.
• If you had 100 ETH on that bridge and the bridge got hacked, your 100 ETH is no longer safe because the attacker can drain money out of the bridge.
• The problem gets worse when you add more blockchain networks into the mix
• If you have 100 chains with bridges to each other, a 51% attack on even one of those chains risks contagion that could spread to all 100 chains