Abstract: An identities collaboration system that comprises a Personal Service Provider (PSP) system for supplying specific user related personal service(s); means for assigning two different data files to each user opting-in to the PSP system, wherein one data file contains data representing the user identity at the PSP system and it assigned on a first domain, and the other data file(s) contains data representing the information regarding whether the user is opted-in, or another identity number that is related to the user identity at the PSP, and is assigned on a second domain.