A mobile communication device operates in a wireless communication network with use of a communication service provided by a service provider (e.g. a wireless carrier for voice telephony, or data service provider for data synchronization). An application server receives, via the wireless network, a message from the mobile device. The message has a field for inclusion of a token having a digital signature corresponding to the service provider. The application server performs token validation of the message, which includes a verification step for verifying the digital signature of the token with a public key corresponding to the service provider. The application server then grants or denies access to an application service depending on the outcome of the token validation. In one embodiment, the application service is an e-commerce transaction service, wherein a proof-of-work (POW) test (e.g. a Captcha test) otherwise utilized for the service is bypassed or excluded.