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by cgjaro 4296 days ago
I don't know if "10 years" falls in your definition of "next few years".

For a viable rogue CA attack, you need a chosen-prefix attack. Current best research (https://marc-stevens.nl/research/papers/EC13-S.pdf) shows it should take 2^77.1 SHA-1 compression calls to do a chosen-prefix attack. Say this is improved to 2^65 within the next 10 years. Right now a good GPU (AMD R9 290) can do 3 billion SHA-1 compression calls per second. Say Moore's Law continues for the next 10 years and that 10 years from now a GPU can do 20 billion SHA-1 per second. So 10 year from now, 100 high-end GPUs should be able to produce a rogue CA with colliding SHA-1 signature in 7 month of compute time.

Change one little assumption and assume the best attack ends up being 2^60 instead of 2^65. In this case, a viable attack could certainly be carried out in the next 3-4 years.

You can't cross your fingers and hopes such an attack will not be discovered. The time to abandon SHA-1 is now.

2 comments

Firstly, GPUs haven't followed More.

Secondly, multiple sha1 ASIC exists.

Thirdly, WebGL has made it trivial to gain vast GPU resources. 20,000 viewers for two hours can be bought for $20.

Fourthly, I don't care.

> Firstly, GPUs haven't followed More.

Yes they have. Any integrated circuit that tries to pack as many transistors as possible on a die is, by definition, following Moore's Law. To convince you: http://www.mumblegrumble.com/visual/roadmap/other/nvidia_moo...

> 20,000 viewers for two hours can be bought for $20

Is that pricing from a botnet or a company like crowdprocess.com?

I agree.