Software developed by S.R.D. (Systems Research and Development), recently acquired by IBM, allows huge collections of personal data (travel manifests, medical data) to be compared with other databases, such as terrorist watch lists, while not actually disclosing the data between two entities. What’s actually compared is a one-way hash, and any “hits” between two lists, would identify a record number that would presumably lead to a request for the whole record. S.R.D. was originally funded by the CIA’s In-Q-Tel venture capital arm.