Why it’s harder to forge a SHA-1 certificate than it is to find a SHA-1 collision

What this post added

This post explains why forging a SHA-1 certificate is significantly harder than finding a SHA-1 collision. It details the mechanics of digital signatures, the security properties of hash functions (collision resistance, second pre-image resistance, pre-image resistance), and how MD5 collisions were exploited using chosen-prefix attacks to forge certificates. The post highlights the importance of strong cryptographic primitives for maintaining trust on the internet and the ongoing efforts to deprecate insecure algorithms like SHA-1, contributing to the broader theme of securing web infrastructure.