BLOCKCHAIN BASED ACCESS CONTROL USING TIME-DEPENDENT OBFUSCATION OF ACCESS TOKENS

There is provided a computer-implemented method for managing third-party access to data, to increase data security and/or privacy. The method comprises receiving, from a third-party computer, a request to access data, wherein the request is indicative of at least one requested operation. A validity of each of the requested operations is determined in dependence on permission data stored in a distributed public ledger. The permissions data defines, for said third-party computer, a set of permissible operations and one or more permissible data attributes associated with each of the set of permissible operations. The request and the validity are logged in the distributed public ledger. For each of the requested operations, if the requested operation is valid, there is created, on the public ledger, an electronic token enabling the third-Valid party computer to obtain access to one or more of the permissible data attributes associated with the requested operation, wherein the electronic token comprises information indicative of a location of the data attributes. A time-dependent transformation is applied to an element of the electronic token, and the electronic token is communicated from the public ledger to the third-party computer.