Provided is ad-hoc creation of groups based on contextual information comprising. Two mechanisms are used to restrict valid members of a group. First, to make sure that devices are somehow related, devices provide contextual information that is compared to the contextual information provided by other devices willing to join the group. Only devices providing "similar" contextual information are accepted as possible candidates in the group. Second, to scope the group, a time window is used to limit the duration of the group creation. In other words, access to the group is reserved to the devices that can provide similar context information to existing member of the group in a defined time window. Security properties are ensured by enabling a visual check of the list of group participants. For instance, a member can verify that the displayed pictures indeed represent the attendees of an ongoing meeting.