A transaction verification process performed by a transaction network operator in communication with a client computing device and a third party provider. A computing device may be equipped with an integrity verification module for verifying the system integrity of the computing device, and a cryptographic module for digitally signing transaction requests. The transaction network operator may verify that transaction requests processed by the third party provider are properly associated with a valid computing device by verifying signatures from the cryptographic module and the integrity verification module. In response to a request from the third party provider, the transaction network operator may verify that the computing device is authorized to complete the transaction by challenging the computing device for proper credentials. The transaction network operator may verify the credentials provided by the client device and indicate to the third party provider that the transaction is valid.