Provided is a process that affords out-of-band authentication based on a secure channel to a trusted execution environment on a client device. The authentication process includes one or more authentication steps in addition to verifying any credentials provided by a client device. A notification may be transmitted by a server to a device other than the client device attempting to access the asset. That device may be a mobile device with a trusted execution environment storing user credential information, and the server may store representations of those credentials. The mobile device collects user input credentials and transmits representations for matching the previously stored representations and signed data for verification by the server that received data originated from the mobile device. The access attempt by the client is granted based in part on the result of authenticating the data received from the mobile device in a response to the notification.