Stop using SHA1: It’s now completely unsafe

Lucian Constantin

"Moving forward, it’s more urgent than ever for security practitioners to migrate to safer cryptographic hashes such as SHA-256 and SHA-3," Google said in a blog post Thursday. "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."

Starting with version 56, released this month, Google Chrome will mark all SHA-1-signed HTTPS certificates as unsafe. Other major browser vendors plan to do the same.

"Hopefully these new efforts of Google of making a real-world attack possible will lead to vendors and infrastructure managers quickly removing SHA-1 from their products and configurations as, despite it being a deprecated algorithm, some vendors still sell products that do not support more modern hashing algorithms or charge an extra cost to do so," said David Chismon, senior security consultant at MWR InfoSecurity. "Whether this happens before malicious actors are able to exploit the issue for their benefit remains to be seen."

More information about the attack, which has been dubbed SHAttered, is available on a dedicated website and in a research paper.

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