Cryptographic hash functions are one of the building blocks of modern computing systems. Although they were originally developed for signing digital signatures with public key cryptography, they have found uses in digital forensics, digital timestamping, and cryptocurrency schemes like Bitcoin.
Cryptographic hash functions like MD5, SHA-1, and BLAKE3 are widely used and appreciated by programmers, end users, and even lawyers! Nevertheless, I'll start off this column with a basic description of what hash functions are and the hash functions that are used today. Then I'll delve back to the first references to them that I've been able to find and give a bit of their history. I'll briefly touch on their uses in cryptography and then discuss how they also found use in digital forensics. I'll end with a puzzle from Stuart Haber, one of the co-inventors of the blockchain concept. Unless otherwise noted, all of the timing runs were performed on my Mac mini (vintage 2018) with a six-core Intel Core i5 processor running at 3 GHz. The hashing was done with OpenSSL 1.1.1d, compiled September 10, 2019, that ships with the Anaconda Python distribution.
