Restricted-use authentication codes

On a network-accessible service, a method of authenticating a first device via a restricted-use authentication code, the method comprising:

• receiving a request for a restricted-use authentication code from a second device associated with a user;
• generating the restricted-use authentication code;
• sending the restricted-use authentication code to the second device;
• receiving from the first device an authentication request comprising the restricted-use authentication code;
• authenticating the first device as associated with the user based upon receiving the restricted-use authentication code;
• and
• expiring the restricted-use authentication code after authenticating the first device.

A computing system comprising:

• an image sensor;
• a logic machine;
• and
• a storage machine storing instructions executable by the logic machine to:
• detect, via the image sensor, an image of a representation of authentication information displayed via a mobile device;
• decode the representation to determine the authentication information, the authentication information comprising a restricted-use authentication code;
• send, to a network-accessible service, an authentication request comprising the restricted-use authentication code;
• and
• associate a user to the computing system if a confirmation of the authentication request is received from the network-accessible service.