> A preimage attack is what you worry about if you think the person giving you the signature might be untrustworthy, e.g., they're currently promising one thing

> A preimage attack is what you worry about if you think the person giving you the signature might be untrustworthy, e.g., they're currently promising one thing but they might swap it out with something else later. A collision attack is what you worry about even if you don't think the person giving you the signature is untrustworthy and you're expecting someone else to swap out the document before it gets to you You mean vice versa right? Untrustworthy person: could make a collision before giving you the input and mess you around. Trustworthy person doesn't do that (because they are trustworthy). But someone might find a second pre-image attack and do it later on