More specifically, how much wall-clock time did it take, and what was the cost in dollars of the computing power involved?

From shattered.io I see that it took 6500 CPU-years + 110 GPU-years, which tells me roughly how much computing power but nothing about wall-clock time.

This page contains almost what I'm looking for, and it's even from the researchers involved in SHAttered, but it's an estimate dated from late 2015 based on their research up to that point:

Concretely, we estimate the SHA-1 collision cost today (i.e., Fall 2015) between 75K$ and 120K$ renting Amazon EC2 cloud computing over a few months.

Are there up-to-date numbers on what the cost of the actual attack was?

  • 3
    According to the paper, $560,000 in CPU time and $110,000 in GPU time.
    – Xander
    Commented Feb 24, 2017 at 16:37
  • 3
    Xander, the $560k and $110k cost in the paper both refer to the same "second more expensive phase of the attack", depending on whether the attacker waits for cheaper EC2 time when the price is lower. Though it didn't cost them this as they used google's CPU and GPU clusters. (Note the first phase cost 2^60 effort twice and the second phase took 2^63, so roughly 4 times harder).
    – dr jimbob
    Commented Feb 24, 2017 at 17:04
  • Does it really make a difference, though? If Google told you that with their infrastructure it took them one week, how does that help? Commented Feb 24, 2017 at 22:34
  • It takes a CPU approximately 65,000 years and a GPU around 100 years, it'll take a nation-state-level attack to make it anything worth while for the next ten years.
    – Henry F
    Commented Feb 25, 2017 at 1:47

1 Answer 1


Here's the estimates, as quoted by Ars Technica

The first phase of the attack was run on a heterogeneous CPU cluster that was hosted by Google and spread over eight physical locations. A second and more expensive phase was run on a heterogeneous cluster of K20, K40, and K80 GPUs that were also hosted by Google. Had the researchers performed their attack on Amazon's Web Services platform, it would have cost $560,000 at normal pricing. Had the researchers been patient and waited to run their attack during off-peak hours, the same collision would have cost $110,000. That's within the $75,000 to $120,000 range CWI's Stevens projected in late 2015.

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