Method and device for establishing a communication session

Abstract

Devices are provided with secret information to indicate which other devices are eligible to establish communication sessions. Information leaks about the eligibility of devices are prevented when no communication sessions are established. Each device makes a set of preference information items publicly available. Each preference information item selects an eligible device in cloaked way. Each protected information item contains protected information such as an encrypted random number that can be decrypted only by the eligible device. When a request to establish a communication is processed by a first and second device, the first and second device indicate which of their preference information items should be used. The devices then each attempt to decrypt the protected information from the other one's indicated preference information item and each combines the result with the protected information used to make the preference information item that it indicated to the other. The results from the first and second device are compared and when a match is detected, establishment of the communication session is enabled. If no match is detected a first device that did not make the second device eligible is unable to detect whether it was made eligible by the second device.