Control of access by a requesting entity to an asset includes defining an approved state of the requesting entity. A validation of a representation of the approved state of in a non-repudiatable form in obtained from an event validation system. The requesting entity is triggered to determine its current state by an access-control entity, which compares the current state with the approved state and allows access by the requesting entity to the asset only if the current state is the same as the approved state. In a pre-authorization procedure, one or both of the entities issues a data set challenge to the other, which then validates the challenge via the event validation system and returns this validation to the challenging entity, which then checks the validation to see if it is correct. Data sets may be validated, for example, with hash tree based signatures or blockchain entries.