Authorization of another device for participation in multi-factor authentication

1. A method, comprising:

generating, by a computing system, an authentication decision for a multi-factor authentication process for a first account, wherein generating the authentication decision includes communicating with a first mobile device as a factor in the multi-factor authentication process;

in response to a request to authorize participation of a second mobile device as a factor in the multi-factor authentication process for the first account, the computing system generating a secret and transmitting the secret to the first mobile device;

receiving, by the computing system, information from the second mobile device, wherein the information is generated based on capturing an image of a display by the first mobile device, wherein the display is based on the transmitted secret;

verifying, by the computing system, content of the information using the secret;

verifying, by the computing system, that the information is received within a determined time interval from transmitting the secret to the first mobile device;

based on the verification of the content and the time interval, authorizing participation of the second mobile device as a factor in the multi-factor authentication process for the first account; and

based on the authorizing, communicating with the second mobile device as a factor in a subsequent multi-factor authentication process for the first account.

2. The method of claim 1 , further comprising:

verifying that the secret has not been used more than a threshold number of times, wherein the secret is a limited-use secret.

3. The method of claim 1 , further comprising:

receiving, from the first mobile device, configuration information that indicates one or more parameters for use of the second mobile device in the multi-factor authentication process.

4. The method of claim 3 , wherein the configuration information specifies whether both of the first and the second mobile devices are to participate in the multi-factor authentication process.

5. The method of claim 3 , wherein the configuration information specifies a type of authentication to request from the second mobile device for the subsequent multi-factor authentication process.

6. The method of claim 1 , wherein the display is an image of a two-dimensional pattern generated based on the secret.

7. The method of claim 1 , wherein the authentication factor is a non-first factor of the multi-factor authentication process.

8. A non-transitory computer readable medium having instructions stored thereon that are capable of being executed by a computer system to perform operations comprising:

generating an authentication decision for a multi-factor authentication process for a first account, wherein generating the authentication decision includes communicating with a first mobile device as a factor in the multi-factor authentication process;

in response to a request to authorize participation of a second mobile device as a factor in the multi-factor authentication process for the first account, generating a secret and transmitting the secret to the first mobile device;

receiving information from the second mobile device, wherein the information is indicated as pertaining to the request to authorize participation of the second mobile device and is generated based on capturing an image of a display by the first mobile device, wherein the display is based on the transmitted secret;

verifying content of the information using the secret;

verifying that the information is received within a determined time interval from transmitting the secret to the first mobile device;

based on the verification of the content and the time interval, authorizing participation of the second mobile device as a factor in the multi-factor authentication process for the first account; and

based on the authorizing, communicating with the second mobile device as a factor in a subsequent multi-factor authentication process for the first account.

9. The non-transitory computer readable medium of claim 8 , wherein the secret is a limited-use secret, wherein the operations further comprise verifying that the secret has not been used more than a threshold number of times.

10. The non-transitory computer readable medium of claim 8 , wherein the operations further comprise:

receiving, from the first mobile device, configuration information that indicates one or more parameters for use of the second mobile device in the multi-factor authentication process.

11. The non-transitory computer readable medium of claim 10 , wherein the configuration information specifies whether both of the first and the second mobile devices are to participate in the multi-factor authentication process.

12. The non-transitory computer readable medium of claim 10 , wherein the configuration information specifies a type of authentication to request from the second mobile device for subsequent multi-factor authentication process.

13. The non-transitory computer readable medium of claim 8 , wherein the display uses a display unit of the first mobile device and is an image of a two-dimensional code generated based on the secret.

14. The non-transitory computer readable medium of claim 8 , wherein the authentication factor is a non-first factor of the multi-factor authentication process.

15. The non-transitory computer readable medium of claim 8 , wherein the operations further comprise:

in response to a request to authorize participation of a third mobile device as a factor in the multi-factor authentication process, transmitting a second secret to the second mobile device;

receiving information from the third mobile device, wherein the information is indicated as having been generated based on capturing an image of a display by the second mobile device; and

verifying the information based on the second secret and the determined time interval.

16. The non-transitory computer readable medium of claim 8 , wherein the secret is encrypted before it is sent to the first mobile device.

17. A non-transitory computer readable medium having instructions stored thereon that are capable of being executed by a computing device to:

capture an image of a visual pattern displayed by a mobile device to authorize participation of the computing device as a factor in a multi-factor authentication process for a first account, wherein the mobile device is previously authorized to participate as a factor in the multi-factor authentication process and wherein the visual pattern is based on a secret transmitted to the mobile device from an authentication server;

process the captured image and send information to the authentication server based on the captured image as evidence of physical proximity to the mobile device; and

based on verification by the authentication server of the information, receive a request as a factor in a subsequent multi-factor authentication process for the first account.

18. The non-transitory computer readable medium of claim 17 , wherein the instructions are further executable to:

request authorization for participation of another mobile device in the multi-factor authentication process for the first account; and

display a visual pattern based on a secret received from the authentication server in response to the request.

19. The non-transitory computer readable medium of claim 17 , wherein processing the captured image includes determining the secret based on the visual pattern, wherein the information includes the secret.

20. The non-transitory computer readable medium of claim 17 , wherein the received request is a non-first factor in the multi-factor authentication process for the first account.