Direct Integration with Ethereum

[lastmjs]

My original question was posted on the Bitcoin integration thread:

Direct Integration with Bitcoin

My main question with the Bitcoin and Ethereum integration is how the interaction from Bitcoin/Ethereum → IC happens securely, without a bridge, given that Bitcoin and Ethereum do not have a chain key. My concerns are raised in this Twitter thread, and Dominic gives an answer but I would love more details: https://twitter.com/lastmjs/status/1422606758594416645?s=20