This is kinda how Google's Safe Browsing[1] works, although with a few extra layers, such as (IIRC) always requesting some random hashes when confirming matches

This is kinda how Google's Safe Browsing[1] works, although with a few extra layers, such as (IIRC) always requesting some random hashes when confirming matches. I read a better explanation on a mozilla mailing list once, but the key point is that it tries /really/ hard not to disclose private data. [1] https://developers.google.com/safe-browsing/developers_guide_v3#Overview https://developers.google.com/safe-browsing/developers_guide...