US Patent 10102233 Indexing for database privacy and anonymization

An indexing system uses a cascade of hash structures to process data entries upon ingest for indexing. The indexing system may be used for enhancing database privacy, anonymization, or data compression. A hash structure, for example, a bloom filter or hash table, passes a representation of the data entries to a subsequent hash structure in the cascade responsive to determining that the hash structure previously filtered an instance of the same representation. The indexing system can generate the representations of the data entries using one or more hash functions. A terminal hash structure of the cascade may index the data entries responsive to determining that the data entries satisfy a criteria for anonymization. For instance, the indexing system determines that there exists a threshold number of data entries describing a population of subjects having the same combination of data elements.