Verification of identity based signatures

11 1 A database management system comprises up to fifty or more workstations, each for a user. The environment may, for example, be a hospital and the system manages medical records in a secure manner. Each user has a private key issued by a KGC. A database controller updates a secure database with data and associated signatures generated by the user workstations. Thus every record of the secure database has a signature to provide full traceability and non-repudiation of data edits/updates. It is important for the system that the signatures are verified on a regular basis, say every hour. Such a task would be extremely processor-intensive if the database is large. However this is performed by a verification processor of the system in a much shorter time than heretofore, t+n(&Dgr;), where tis the time for one verification, n is the number of signatures, and &Dgr; is a time value which is a very small proportion of t(less than 1%).