A method and apparatus for obtaining access to services of service providers. In one embodiment, the method comprises requesting a desired service through a foreign service provider. (101), generating a hash tree and generating a digital signature on a root value of the hash tree (102), sending the digital signature and the root value to the foreign service provider (103), providing one or more tokens to the foreign service provider with the next packet if the foreign service provider accepts the signature (105) and continuing to use the service while the foreign service provider accepts token (107).