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Google Has Demonstrated a Successful Practical Attack Against SHA-1 (googleblog.com)
Reader Artem Tashkinov writes: Ten years after of SHA-1 was first introduced, Google has announced the first practical technique for generating an SHA-1 collision. It required two years of research between the CWI Institute in Amsterdam and Google. As a proof of the attack, Google has released two PDF files that have identical SHA-1 hashes but different content. The amount of computations required to carry out the attack is staggering: nine quintillion (9,223,372,036,854,775,808) SHA1 computations in total which took 6,500 years of CPU computation to complete the attack first phase and 110 years of GPU computation to complete the second phase.
Google says that people should migrate to newer hashing algorithms like SHA-256 and SHA-3, however it's worth noting that there are currently no ways of finding a collision for both MD5 and SHA-1 hashes simultaneously which means that we still can use old proven hardware accelerated hash functions to be on the safe side.
Google says that people should migrate to newer hashing algorithms like SHA-256 and SHA-3, however it's worth noting that there are currently no ways of finding a collision for both MD5 and SHA-1 hashes simultaneously which means that we still can use old proven hardware accelerated hash functions to be on the safe side.
It is all about cost-benefit. CPU speeds continue to get faster, and renting CPU time on cloud providers become cheaper and cheaper.
Why is this significant? There are still major certificate authorities out there with intermediate certificates using SHA-1. Find a collision for these certificates, and you essentially become a new intermediate certificate authority with the ability to issue domain certs for basically anything you want and they'll validate in browsers.
Now thing of government agencies or crime syndicates that could afford the CPU/GPU time to do this. It is a highly practical attack vector now.