Unless you’ve been living under a rock, you heard that some researchers managed to create a SHA-1 collision. The short story as to why this matters is the whole purpose of a hashing algorithm is to make it impossible to generate collisions on purpose. Unfortunately though impossible things are usually also impossible so in reality we just make sure it’s really really hard to generate a collision. Thanks to Moore’s Law, hard things don’t stay hard forever. This is why MD5 had to go live on a farm out in the country, and we’re not allowed to see it anymore … because it’s having too much fun. SHA-1 will get to join it soon.
The details about this attack are widely published at this point, but that’s not what I want to discuss, I want to bring things up a level and discuss the problem of algorithm deprecation. SHA-1 was basically on the way out. We knew this day was coming, we just didn’t know when. The attack isn’t super practical yet, but give it a few years and I’m sure there will be some interesting breakthroughs against SHA-1. SHA-2 will be next, which is why SHA-3 is a thing now. At the end of the day though this is why we can’t have nice things.
A long time ago there weren’t a bunch of expired standards. There were mostly just current standards and what we would call “old” standards. We kept them around because it was less work than telling them we didn’t want to be friends anymore. Sure they might show up and eat a few chips now and then, but nobody really cared. Then researchers started to look at these old algorithms and protocols as a way to attack modern systems. That’s when things got crazy.
It’s a bit like someone bribing one of your old annoying friends to sneak the attacker through your back door during a party. The friend knows you don’t really like him anymore, so it won’t really matter if he gets caught. Thus began the long and horrible journey to start marking things as unsafe. Remember how long it took before MD5 wasn’t used anymore? How about SSL 2 or SSHv1? It’s not easy to get rid of widely used standards even if they’re unsafe. Anytime something works it won't be replaced without a good reason. Good reasons are easier to find these days than they were even a few years ago.
This brings us to the recent SHA-1 news. I think it's going better this time, a lot better. The browsers already have plans to deprecate it. There are plenty of good replacements ready to go. Did we ever discuss killing off md5 before it was clearly dead? Not really. It wasn't until a zero day md5 attack was made public that it was decided maybe we should stop using it. Everyone knew it was bad for them, but they figured it wasn’t that big of a deal. I feel like everyone understands SHA-1 isn’t a huge deal yet, but it’s time to get rid of it now while there’s still time.
This is the world we live in now. If you can't move quickly you will fail. It's not a competitive advantage, it's a requirement for survival. Old standards no longer ride into the sunset quietly, they get their lunch money stolen, jacket ripped, then hung by a belt loop on the fence.