Secure data provision method and apparatus and data recovery method and system

To control access to target data whilst relieving the data provider of policing obligations, the data provider provides the target data in encrypted form to a requesting party as part of a data set with which first and second trusted authorities are associated in a non-subvertible manner. Recovery of the target data in clear by the party requires the first trusted authority to verify that a specific individual is a professional accredited with it, the second trusted authority to verify that a particular organisation is accredited with it, the particular organisation to verify that the specific individual is engaged by it, and at least one of the particular organisation and the first trusted authority to verify that the party is the specific individual. Various ways of encrypting the target data are provided, the preferred ways being based on Identifier-Based Encryption schemas.