Generating a first signature value corresponding to a first dataset stored in a first data region having a first access permission level. Determining a signature anonymization value. Truncating the first signature value based on the signature anonymization value. Generating a secure search query for identifying, based on the truncated first signature value, second signature values corresponding to entries of a second dataset stored in one or more second data regions having one or more second access permission levels. Receiving a response to the secure search query including the plurality of second signature values. Determining the entries of the second dataset from the second signature values. Comparing the respective entries of the second dataset to the at least a portion of the first dataset. Generating one or more notifications based on the comparisons indicating a potential match between a particular respective entry of the second dataset and the at least a portion of a first dataset.