Bridges - why do they keep getting hacked?

We’ve discussed lots of different blockchain networks. Now we have to figure out if these networks are going to be at each other's throats, or if they can play nice together.
That’s where bridges come in.
Bridges are used to connect two different blockchain networks. Let's say you have some assets on the Ethereum network but you would like to trade them for something on Solana. You'd need to use a bridge to do this. First, you would use a bridge to transfer your asset from the Ethereum network to the Solana network. Once it is on the Solana network, you would be able to trade it.


Here are just a sample of the many, many blockchain bridges that have been hacked:
  • The Binance Bridge was hacked for $566 million
  • The nomad bridge was hacked for $200 million
  • Axie Infinity (the popular online crypto game) had its Ronin Bridge hacked for $625 million
  • The Solana Wormhole bridge was hacked to the tune of $325 million
Chainalysis estimates that $2 billion has been stolen from bridges in 2022 alone.

Why so weak?

As stories like these keep popping up, Vitalik's post about the fundamental weaknesses of bridges is worth going back to. It's quite heavy reading for a Reddit post, so here's the summary:

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