A method of authentication of a user is provided. The method comprises capturing a brain activity signal from a user; comparing the brain activity signal with reference data; and determining, based at least in part on the comparison, whether the identity of the user can be confirmed. Also provided is a computing device comprising at least one processor and at least one memory. The computing device is adapted to: communicate with a brain activity sensing system to capture a brain activity signal from the user; provide the captured brain activity signal to an authentication service computing system; and authenticate the user based at least in part on the result of a comparison with reference data received from the authentication service computing system. A system comprising the computing device and a brain activity sensing system, and am authentication service computing device are also provided.