News for hackers. Stuff that matters.

A comment on The first chosen-prefix collision for SHA-1. Parent comment

Re:The first chosen-prefix collision for SHA-1 by ReidZB on Tuesday January 07, 2020 @04:55PM (#21985390)
DES is a good example here: it was designed ~45 years ago and it's still theoretically surprisingly strong when you compare it with other areas of cryptography. By that, I mean it's held up very well to cryptanalysis that attempts to find faster-than-brute-force techniques, with the best attack taking 2^43 time (vs. the 2^56 brute-force time).

To be clear, 2^56 is trivially brute-force-able today, but that can be mitigated with constructs like 3DES, which are still (barely) secure despite being based on a 45-year-old cipher.

(So no one mistakes my intent, there are many reasons to prefer AES over DES. I just wanted to provide it as an example, especially since it happened to line up with the 40-year timeframe.)

[ Parent | on HN ]
Re:The first chosen-prefix collision for SHA-1 by zwp on Tuesday January 07, 2020 @07:47PM (#21987051)
> 2^56 is trivially brute-force-able today

Youch, this broke my intuition.

https://crack.sh/

"we’ve built a system with 48 Virtex-6 LX240Ts which can exhaust the keyspace in around 26 hours"

[ Parent | on HN ]
Re:The first chosen-prefix collision for SHA-1 by tgsovlerkhgsel on Tuesday January 07, 2020 @08:24PM (#21987298)
> trivially

Having to rent thousands of dollars in GPU-hours or using specialized hardware doesn't sound "trivial" to me. Practical, yes. Accessible even to a layman with money to spare, yes. Trivial? Hell no.

[ Parent | on HN ]
Re:The first chosen-prefix collision for SHA-1 by userbinator on Tuesday January 07, 2020 @11:00PM (#21988171)
It's funny to see how different the various people here have on the definition of "trivial". 10 years ago, I generated MD5 collisions in a few minutes with a tiny little executable I downloaded. That's what I call trivial.

If I had some DES-encrypted files that I'd lost the key to, and they were important enough that I needed their contents, I would probably be happy that I could crack the key today and recover them if I spent enough, but doing so would still not be "trivial".

[ Parent | on HN ]
Re:The first chosen-prefix collision for SHA-1 by ReidZB on Wednesday January 08, 2020 @12:49AM (#21988707)
Oh, sure, maybe trivial isn't the best word for it, but it's all relative (to me). $20k is remarkably cheap for a practical cryptographic attack compared to the rest of the field, and there's plenty of software to do it, and it's been done before (many times).

Apparently there's even a SaaS offering to do it for you in some cases (for staggeringly cheap, like $300), but I had no idea that existed when I wrote my comment.

[ Parent | on HN ]