> It doesn't work retroactively. That crud needs to be there in the initial commit when it's accepted by multiple people. Do you assume that a proper preimage-

> It doesn't work retroactively. That crud needs to be there in the initial commit when it's accepted by multiple people. Do you assume that a proper preimage-attack would be needed? Instead, the good looking object could be committed, I guess after reading https://news.ycombinator.com/item?id=13721237 https://news.ycombinator.com/item?id=13721237 edit: > And that bugfix would have to have a blob of crud in the 'good' version Looking at google's POC, the colliding pdfs don't at all stick out (edit: but they are horribly contrived and you talked about code not blobs) [https://shattered.io/ https://shattered.io/] edit: thanks for your answer, it motivated me to learn a bit more. I'm still not sure if "never" is a rounding error, hyperbole (which would be ill advised talking to laymen), or actual fact (that source files due to the reduced entropy in byte patterns could in fact never ever collide, which I doubt).