per minute or per data amount basis that the wlan 20 expects to charge the user and hence the rate of reimbursement expected from billing agent 26 upon finding the contract terms acceptable the billing agent 26 sends back a signed contract or such other acknowledgement during step 104 the contract can be signed digitally by machine rather than by a human being next the wlan 20 requests from the billing agent 26 its digital certificate during step 106 whereupon the billing agent delivers the certificate to the wlan 20 during step 108 the billing agent 39 s digital certificate constitutes a data file that includes the public key of the billing agent which a receiving entity i e the user can use to encrypt information for decryption by the billing agent thus allowing for information exchange in a secure manner the wlan 20 forwards the billing agent 39 s certificate to the user during step 110 thereafter the wlan 20 sends to the user the proposed wsr after receiving the billing agent 39 s certificate and the wsr the user then decides whether to accept the access charges demanded by the wlan 20 if the user accepts then during step 114 the user does the following 1 verifies the certificate 2 inputs a pin and 3 encrypts the pin in accordance with the billing agent 39 s certificate the user verifies the certificate using a trusted party 39 s public key to make sure that 1 the certificate is indeed issued by the trusted party and 2 the certificate hasn 39 t been altered by anybody else encryption of the pin in accordance with the billing agent 39 s certificate entails encrypting the pin.