> If we move all crypto to purpose-made hardware, someone could just start trying to target the messages to/from the crypto system.
This is one of the technical advantages of a blockchain-based system. As long as the keys are protected and signatures are generated in a secure environment, then the content of the message doesn't need to be secret to be secure.
It's not a solution to situations where privacy is desired, but if the reason for secrecy is simply to ensure that transactions are properly authorized (by avoiding the leakage of passwords and session information) then keeping the signature process secure should be sufficient even where general secrecy cannot be maintained.
This is one of the technical advantages of a blockchain-based system. As long as the keys are protected and signatures are generated in a secure environment, then the content of the message doesn't need to be secret to be secure.
It's not a solution to situations where privacy is desired, but if the reason for secrecy is simply to ensure that transactions are properly authorized (by avoiding the leakage of passwords and session information) then keeping the signature process secure should be sufficient even where general secrecy cannot be maintained.