Google Online Security Blog: Announcing the first SHA1 collision

Announcing the first SHA1 collision

23 февруари 2017 г.

Posted by Marc Stevens (CWI Amsterdam), Elie Bursztein (Google), Pierre Karpman (CWI Amsterdam), Ange Albertini (Google), Yarik Markov (Google), Alex Petit Bianco (Google), Clement Baisse (Google)attacks on the mathematical underpinningsCWI Institute in Amsterdamreleasing two PDFsannouncedWhat is a cryptographic hash collision?

Finding the SHA-1 collision
Marc StevensPDF prefix

Nine quintillion (9,223,372,036,854,775,808) SHA1 computations in total

6,500 years of CPU computation to complete the attack first phase

110 years of GPU computation to complete the second phase

While those numbers seem very large, the SHA-1 shattered attack is still more than 100,000 times faster than a brute force attack which remains impractical.
Mitigating the risk of SHA-1 collision attacks
Moving forward, it’s more urgent than ever for security practitioners to migrate to safer cryptographic hashes such as SHA-256 and SHA-3. Following Google’s vulnerability disclosure policy, we will wait 90 days before releasing code that allows anyone to create a pair of PDFs that hash to the same SHA-1 sum given two distinct images with some pre-conditions. In order to prevent this attack from active use, we’ve added protections for Gmail and GSuite users that detects our PDF collision technique. Furthermore, we are providing a free detection system to the public.
You can find more details about the SHA-1 attack and detailed research outlining our techniques here.
About the team
This result is the product of a long-term collaboration between the CWI institute and Google’s Research security, privacy and anti-abuse group.
Marc Stevens and Elie Bursztein started collaborating on making Marc’s cryptanalytic attacks against SHA-1 practical using Google infrastructure. Ange Albertini developed the PDF attack, Pierre Karpman worked on the cryptanalysis and the GPU implementation, Yarik Markov took care of the distributed GPU code, Alex Petit Bianco implemented the collision detector to protect Google users and Clement Baisse oversaw the reliability of the computations.

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Announcing the first SHA1 collision

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