Purpose-restricted Anonymous Mobile Communications Using Anonymous Signatures in Online Credential Systems

To avoid the risk of long-term storage of secrets on a portable device, an online credential system supports the roaming user in retrieving securely at various locations his private key and other material to generate anonymous signatures. The protocol proposed here allows a roaming mobile user to access anonymously services such as whistle blowing and net-counselling. Our approach: (1) allows a mobile user, remembering a short password, to anonymously and securely retrieve the credentials necessary for his anonymous communication without assuming a pre-established anonymous channel to the credential server or establishing an anonymous channel using the time-consuming existing rerouting techniques; (2) provides authenticated anonymous access to privacy-related services without rerouting the packets; (3) helps combatting the abuse of anonymity for performing illegal activities (e.g. redistribution of copy-righted contents, illegal drug trading and so on).