Techniques for secure voice authentication. In one example, a method includes the following steps. A first computing device initiates establishment of a secure channel between the first computing device and a second computing device. The first computing device includes a trusted device and the second computing device at least partially hosts a service that a user of the trusted device seeks to access. A prompt is received at the first computing device from the second computing device over the secure channel. The prompt requests a user voice response for use in making an authentication decision for the user based on the user voice response.