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Use the cryptopan library to pseudonymize IP address before hashing into HLL #273
Description
To enhance end-user privacy, EDM should encrypt the end-user IP address before hashing into HLL. It should be encrypted with a secret that only the resolver operator knows. The reason for this is that some IP addresses might cause unique patterns in the HLL sketch. Someone with access to a sketch and knowledge of the operator's IP range can generate and use a rainbow table in an attempt to recover some of these addresses from the sketch. Encryption fixes this since it makes the rainbow table impossible to generate.
Getting familiarized with the code around here should be a good implementation starting point:
Line 97 in e351808
Activity
zluudg commentedon Aug 17, 2026
Techdocs should be updated once this feature is properly in place. A PR has been prepared here: https://github.com/dnstapir/techdocs/pull/65
morkrost commentedon Aug 17, 2026
Actually...
We really don't need something as advanced as CryptoPAn, since we don't care about subnets. I would suggest that we remove the CryptoPAn dependency entirely and use 64 bits from a (pick one) cryptographic hash F( key + IPv4 address) instead of Murmur3. Key is equivalent to the key used for CryptoPAn.
Oh, and the same for IPv6, naturally.
zluudg commentedon Sep 17, 2026
Succeeded by #302, will not use cryptopan but AES instead.