>I'm also sure that SHA-1 remains pervasive in many codebases I've done a lot of security reviews of backup solutions over the years and nearly universally the

>I'm also sure that SHA-1 remains pervasive in many codebases I've done a lot of security reviews of backup solutions over the years and nearly universally they use SHA1 for de-duplication. Security professionals have been providing warnings about this practice, but when you are dealing with a cloud backup solution as an example, speed and low compute requirements are a must and it's hard to win the argument when someone tosses "theoretical" onto the table. Well, we are now past "theoretical" and that's what matters. I just tried out the SHA1 collider: https://alf.nu/SHA1 https://alf.nu/SHA1 and created two PDFs containing entirely different bits of text in JPGs. It took seconds and indeed the output of the files were SHA1 identical. This is no longer nation-state level stuff and computing colliding documents to upload to cloud backup providers who de-dupe across the file system and not just restricted within the boundaries of each account could result in the ability to wipe out and change other people's data. At a minimum that could be an annoyance. At worst, it could result in the intentional change of someone's content to cause significant financial or physical harm.