CLK(Cryptographic Linkage Key)

A CLK takes a record's identifying fields (name, date of birth, address, etc.), hashes them through a shared schema with a shared salt, and stores the result as bits in a Bloom filter. Two CLKs that have many bits in common are likely the same person.

Bloom filters are critical here because they're noisy by design: a single CLK leaks very little about the underlying record, but two CLKs from the same person produce highly-overlapping filters. That tolerance for noise is also what makes CLK matching robust to minor typos and formatting differences — the same property that makes traditional fuzzy matching work, applied at the bit level.

CLK is the encoding behind PPRL. The dominant production library is `anonlink-client` (Python + browser).