The shattered prefix was chosen as well, see my other comment in the thread: https://news.ycombinator.com/item?id=21980759 https://news.ycombinator.com/item?id=

The shattered prefix was chosen as well, see my other comment in the thread: https://news.ycombinator.com/item?id=21980759 https://news.ycombinator.com/item?id=21980759 The only thing that prefixing the length makes difficult is using the same prefix multiple times: you basically have to make up your mind about the type and length before mounting the shattered attack. Also, the prefix means you have to do your own shattered attack and can't use the PDFs that google provided as proof of their project's success. Price tag for that seems to be 11k. [1]: https://github.com/cr-marcstevens/sha1collisiondetection https://github.com/cr-marcstevens/sha1collisiondetection