> Whatever is written on blockchain A cannot be considered true in blockchain B without breaking the security model of blockchain B by making blockchain A a tr

> Whatever is written on blockchain A cannot be considered true in blockchain B without breaking the security model of blockchain B by making blockchain A a trusted third-party. To be more specific, when I said "like proof of stake", what I meant is that there's a trusted pool of validators but the individual validators are not assumed to be trustworthy (only the pool in aggregate), and the validators use a adversarial staking model to punish dishonesty. In the case of bridges, that pool is external to the chain. So yes, there is external trust happening. I'll try to address your example, but I've researched this a while ago so I'm sure I could be off the mark. For your example, lets say we're moving A-token in A-chain to wrapped A-tokens in B-chain, so we can easily assume it's a 1:1 exchange rate by construction. User moves 100 A-tokens in A-chain to a bridge smart contract and as data passes the address of their B-chain wallet. A subset of validators in the trusted pool (chosen via some distributed protocol) together sign a multi-sig transaction that authorizes the bridge contract in B-chain to mint 100 wrapped A-tokens and send 99.9 of them to the destination address that the bridging user, and collect 0.1 of them as fee. (If transaction were dishonest, a larger subset of validators would together sign a transaction purging those validators' stake in the pool; so the subset of validators chosen are honest out of desire to keep their staking capital and earn the 0.1 fee) That's at a high level how it works. If you want the full details I recommend finding a technical writeup for a popular trustless bridge.