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Does the server have to multiply the whole 8G block by the encrypted query? If not, wouldn't the server know which block the query was for?

Why return a full row? Wouldn't that leak the hashes of an entire row to every client? Why not set the encrypted query to return just if the password is there or not?

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Yes, the server multiplies the query by the entire 8 GB every time. It’s not as slow as it sounds :-) … it’s basically limited by memory bandwidth.

Yeah, we do return the full row. It does leak the hashes, but these are already public (you can directly download them from the Have I Been Pwned website).

Under the hood, we don’t actually send the full hashes back; we can get away with just sending back fewer bits (enough to minimize the chance of a false positive).

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