A fingerprinting database management system presents a unique version or view of the data to each user. The view contains small pseudorandom modifications to selected data items. The objective of this system is to identify users who divulge proprietary information which they have obtained through legitimate access. Even if the user makes further modifications to the data before its misuse, a statistical procedure will identify the source of misuse with any desired degree of certainty.>

This paper presents two specialized approaches to the design of a database incorporating cryptography in a fundamental way. Most processing is carried out on the encrypted version of the database at an insecure central site. Query initiation and final query interpretation occur at a secure local workstation. The first approach implements a text file with searches based on keywords. The second approach uses subfields and homophonic representations to create a secure database with fairly broad capabilities.

This article suggests the use of undecidable problems in constructing public-key cryptosystems. Any such system must still be in NP, but intuitive arguments suggest that this approach might be a reasonable alternative to the use of NP-complete problems. A general approach based on the undecidable word problem for groups is discussed, though without enough detail to evaluate a specific implementation. The resulting cryptosystem, if successful, would be a randomized public-key encryption procedure with infinitely many ciphertexts corresponding to each plaintext. Also , it is possible that a specific implementation could have infinitely many secret keys corresponding to one public key.

This paper presents a general discussion of the use of fingerprints, especially fingerprinted data, Fingerprinting is classified in four orthogonal ways, and some illustrative examples are given. The basis for a statistical analysis of altered fingerprints is presented, along with an example simulation. The possibility of more subtle fingerprints is discussed.

This article presents a two-stage encryption method for sharing access to a database where no single agency or device can ever encrypt or decrypt the data directly. Thus an attack by an opponent would have to succeed at two separate points. The main tool needed is a secure cryptosystem closed under composition: encrypting and re-encrypting using two successive keys is equivalent to a single encryption using some third key. An example cryptosystem satisfying this condition is exponentiation modulo a fixed prime.