The SHA-1 hash function, which has long been considered insecure, is now officially broken as of yesterday. Given the renewed interest in hash function collisions, I’d like to point out an article I wrote about attacks on secure hash functions, in the hopes that you will find it useful and interesting.
You can can read the full article at https://z.cash/technology/history-of-hash-function-attacks.html.
The main result of this investigation is that a cryptosystem invulnerable to collision attacks is much safer than one that is vulnerable to collision attacks (regardless of whether it is vulnerable to pre-image attacks). Another interesting takeaway is that it looks like sometime between 1996 (Tiger) and 2000 (Whirlpool), humanity might have
learned how to make collision-resistant hash functions, since none of the prominent secure hash functions designed since that era have succumbed to collision attacks. Maybe modern hash functions like SHA-256, SHA-3, and BLAKE2 will never be broken.
As a graphical reference for the article, I’ve included a color-coded chronological view of collision attacks, and of second pre-image attacks, as well as a survey of the best known attacks on secure hash functions.
Thanks to Andreas Hülsing, Samuel Neves, and Zcash engineer Daira Hopwood for their input on this investigation.
