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Understanding Have I Been Pwned's Use of SHA-1 and k-Anonymity

Troy Hunt

Four and a half years ago now, I rolled out version 2 of HIBP's Pwned Passwords that implemented a really cool k-anonymity model courtesy of the brains at Cloudflare. Actually, the multiple problems, the first of which is that it's just way too fast for storing user passwords in an online system. is the middle one.

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