A method of establishing a communication session using a first and second device from a larger plurality of devices in a communication system, wherein each device of the plurality is enabled to use a respective decryption key that is not available to other devices in the plurality, the method comprising; - selecting, for each particular device of the plurality, a subset of eligible devices in the plurality that are eligible for establishing communication sessions; - providing, for each particular device of the plurality, protected information items associated with respective eligible devices in the subset of the particular device, the protected information items being selectively retrievable in the particular device only; - providing, for each particular device of the plurality, a respective set of preference information items for the subset of the particular device, each preference information item comprising the protected information item associated with a respective eligible device in the subset, accessible by means of the decryption key of the respective eligible device; - making the respective sets of preference information items of at least the first and second device available to all of the devices in the plurality; - triggering a communication session establishment process between the first and second device; - indicating a first one of the available preference information items to the first device from the set of the second device; - indicating a second one of the available preference information items to the second device from the set of the first device; - decrypting protected information items from the first and second one of the preference information items in the first and second device using the decryption keys of the first and second device respectively; - retrieving the retrievable protected information item associated with the indicated second and first one of the information items in the first and second device respectively; - deriving match data from a computation of a one way function of a combination of the decrypted and retrieved protected information item in each of the first and second device; - comparing the match data from the first and second devices; - enabling establishment of the communication session if the match data from the first and second devices match with each other. - selecting, for each particular device of the plurality, a subset of eligible devices in the plurality that are eligible for establishing communication sessions; - providing, for each particular device of the plurality, protected information items associated with respective eligible devices in the subset of the particular device, the protected information items being selectively retrievable in the particular device only; - providing, for each particular device of the plurality, a respective set of preference information items for the subset of the particular device, each preference information item comprising the protected information item associated with a respective eligible device in the subset, accessible by means of the decryption key of the respective eligible device; - making the respective sets of preference information items of at least the first and second device available to all of the devices in the plurality; - triggering a communication session establishment process between the first and second device; - indicating a first one of the available preference information items to the first device from the set of the second device; - indicating a second one of the available preference information items to the second device from the set of the first device; - decrypting protected information items from the first and second one of the preference information items in the first and second device using the decryption keys of the first and second device respectively; - retrieving the retrievable protected information item associated with the indicated second and first one of the information items in the first and second device respectively; - deriving match data from a computation of a one way function of a combination of the decrypted and retrieved protected information item in each of the first and second device; - comparing the match data from the first and second devices; - enabling establishment of the communication session if the match data from the first and second devices match with each other.