Method and system for determining proximity between two entities

摘要

A method of determining whether a first entity is within a predefined proximity of a second entity is disclosed. The method comprises generating a set of random number pairs at the first entity, sending from the first entity to the second entity encrypted information from which the second entity can derive the set of random number pairs, decrypting the encrypted information at the second entity, deriving the set of random number pairs at the second entity, sending an acknowledgement from the second entity to the first entity, measuring a first value of time at the first entity, sending from the first entity to the second entity a first number from the set of random number pairs, verifying, at the second entity, that said first number is from the set of random number pairs, sending from the second entity to the first entity, a corresponding random number from said set of random number pairs, receiving the corresponding random number at the first entity, and measuring a second value of time at the first entity. The first entity may be a first computing node (3602) that contains protected content and/or content access material, and the second entity may be a second computing node (3606) remote from the first computing node.