A technique in a mobile device which is configured to communicate in a wireless network with use of a communication service provided by a service provider is described. The mobile device is configured to access via the wireless network a server for execution of an e-commerce transaction. The server is configured to administer a proof-of-work test in order to allow completion of the e-commerce transaction. The mobile device receives via the wireless network a token from a token server. The token is digitally signed by the service provider with a digital signature thereof. The mobile device sends via the wireless network a message to the server, and this message includes the token. When token validation of the message at the server is successful, the mobile device completes the e-commerce transaction with the server without performing the proof-of-work test, which is bypassed for the mobile device.