A method and system for anonymous purchase by a first user device, is described, the method and system including sending R from the first user device to a second user device, where R is a result of a one-way function performed on a random number r selected by the first user device, the second user device being operative to send R to a service provider, which stores R with a data string T and the service provider returns a digitally signed R and T to the second user device, thereby providing the a data string T to the second user device, receiving R and T at the first user device from the second device, thereby ensuring that the identity of the first user device remains unknown to the service provider, opening a communication channel between the first user device and the service provider, sending the service provider r and T from the first user device via the communication channel along with a request for the service provider to provide a service, and receiving the requested service from the service provider. Related methods, systems and apparatus are also described.