A system is provided for cycling encryption keys to prevent the guessing of encrypted presence information in a shared information space. The system of the invention prevents malicious publication of presence information and ensures that only valid presence information is published to the shared information space. A malicious subscriber is prevented from knowing that he/she has been detected while a search is underway to determine his/her identity. During such a search, authorized subscribers are shifted to a new source of presence information while the malicious subscriber remains at the previous source.