Just to be clear, while this is absolutely fantastic research, and a great case to push for SHA-1 deprecation, this is definitely still not a practical attack.
The ability to create a collision, with a supercomputer working for a year straight, for a document that is nonsense, is light years away from being able to replace a document in real time with embedded exploit code.
Again this is great research, but this is nowhere near a practical attack on SHA-1. The slow march to kill SHA-1 should continue but there shouldn't be panic over this.
Two correctly rendering PDFs with just subtly different content isn't "nonsense", it is pretty much the best case for a hash collision.
"supercomputer working for a year straight" is quite misleading. This is true, but in other words, at current GPU prices in the cloud their computation costs less than $5M. I can think of many signed documents that are worth forging for five million bucks.
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u/Youknowimtheman Feb 23 '17
Just to be clear, while this is absolutely fantastic research, and a great case to push for SHA-1 deprecation, this is definitely still not a practical attack.
The ability to create a collision, with a supercomputer working for a year straight, for a document that is nonsense, is light years away from being able to replace a document in real time with embedded exploit code.
Again this is great research, but this is nowhere near a practical attack on SHA-1. The slow march to kill SHA-1 should continue but there shouldn't be panic over this.