When Hashes Collide
Bitcoin operates under certain assumptions, such as an honest majority of computational power. The assumption we discussed in this last lecture was that cryptographic hashes are unique, given the properties of preimage, second preimage, and collision resistance.
Let’s say that you manage to break computer science as we know it and devise a way to make any input look like your preferred output. Formally, you can always construct an input y such that you can control the value of H(y) to be in your favor. You can create collisions at will. How can you then manipulate the Bitcoin protocol in your favor? There are several different answers, but you only need to provide one example.
Feel free to discuss amongst each other in the discussion board topic below. We’ll be grading the responses you paste into the text input.