Remote secure unlock

1. A method for remotely performing secure change of operational mode of a telecommunications device, the method comprising:

establishing a first secure channel between a modem of the telecommunications device and an application executing in an Execution Environment of the telecommunications device;

establishing a second secure channel between the application and a remote server;

enabling the modem in a limited operational mode;

generating a request, by the modem or the application, to verify the validity of a subscriber identity module of the telecommunications device;

retrieving, by the modem, module identification information from the subscriber identity module;

retrieving verification information, by the application and from the remote server, using the second secure channel, sending the module identification information from the modem to the application using the first secure channel, verifying at the application whether the subscriber identity module is valid using the module identification information and the verification information, and sending the verification result from the application to the modem using the first secure channel,

or

retrieving verification information, by the application and from the remote server, using the second secure channel, sending the verification information from the application to the modem using the first secure channel and verifying at the modem whether the subscriber identity module is valid using the module identification information and the verification information,

or

sending the module identification information from the modem to the remote server, verifying at the remote server whether the subscriber identity module is valid using the module identification information and verification information available at the server, sending the verification result from the remote server to the application using the second secure channel, and sending the verification result from the application to the modem using the first secure channel;

responsive to a positive verification of the subscriber identity module transitioning the modem from the limited operational mode to an enhanced operational mode.

2. The method of claim 1 , wherein the application is a trusted application and the Execution Environment is a Trusted Execution Environment.

3. The method of claim 1 , wherein when the verification is performed at the application or modem, the verification information at the telecommunications device is periodically updated from the remote server.

4. The method of claim 1 , wherein the telecommunications device periodically rechecks the verification of the subscriber identity module, and

wherein responsive to a negative re-verification the modem is transitioned from the enhanced operational mode to a limited operational mode.

5. The method of claim 1 , wherein the verification information specifies a first time period and a second time period,

wherein during, and until the end of, the first time period the telecommunications device is in a temporary unlock state where the modem can transition to the enhanced operational mode either without requiring the verification step to be performed or where the verification step is automatically passed, and

wherein at the expiry of the second time period the telecommunications device contacts a remote eligibility server to request an extension of the first time period.

6. The method of claim 5 , wherein the verification information specifies a third time period and after the expiry of the third time period the telecommunications device enters a permanent unlock state where the modem can transition to the enhanced operational mode either without requiring the verification step to be performed or where the verification step is automatically passed.

7. The method of claim 6 , wherein prior to retrieving the verification information the modem is transitioned from the limited operational mode to an enhanced operational mode for a fourth time period, and

wherein subsequent to expiry of the fourth time period the modem is transitioned back from the enhanced operational mode to the limited operational mode if a positive verification that the subscriber identify module has not been made before the expiry of the fourth time period.

8. The method of claim 7 , wherein a determination that the first time period and/or the second time period and/or the third time period and/or the fourth time period has expired is performed by the application optionally using a trusted time source.

9. The method of claim 1 , wherein when the subscriber identity module is detached from the modem, the modem is transitioned to a limited operational mode.

10. The method of claim 1 , wherein either when the subscriber identity module is reinserted into the telecommunications device, or when a second subscriber identity module is inserted into the telecommunications device, the reinserted subscriber identity module or inserted second subscriber identity module must be verified prior to the modem being transitioned from the limited operational mode back to the enhanced operational mode.

11. The method of claim 1 , wherein the telecommunications device has a plurality of subscriber identity modules and the method individually or collectively verifies the validity of all of the subscriber identity modules.

12. The method of claim 1 , wherein one or more of the first and second secure channels are established using Elliptic-curve Diffie-Hellman, Elliptic-curve Diffie-Hellman Ephemeral key exchange or any other asymmetric key sharing algorithm.

13. The method of claim 1 , wherein one or more of the first and second secure channels are established using keys injected to the modem and/or application during manufacture.

14. The method of claim 1 , wherein one or more of the first and second secure channels are established using keys generated by the modem and/or application.

15. The method of claim 1 , wherein two entities at the two ends of the first secure channel and/or two entities at the ends of the second secure channel each maintain a counter which is monotonically incremented upon exchange of messages,

wherein sent messages include a value derived from a sending entity's counter, and

wherein a receiving end entity only accepts as valid messages with the value derived from a counter value higher than a receiving end's current counter value.

16. The method of claim 1 , wherein the request is generated by the application, the application verifies the subscriber identity module, and the application communicates the verification result to the modem via the first secure channel.

17. The method of claim 1 , wherein the request is generated by the modem, the application provides the verification information to the modem by the first secure channel and the modem verifies the subscriber identity module.

18. The method of claim 1 , wherein the module identification information comprises an International Mobile Subscriber Identity “IMSI”, a Group Identifier “GID” or a Subscription Permanent Identifier “SUPI”.

19. The method of claim 1 , wherein when the telecommunications device receives temporary module identification information, a copy of the temporary module identification information is stored on the subscriber identity module and a temporary module identification information authenticator is generated based on the temporary module identification information and an identifier of the telecommunications device, the temporary module identification information authenticator being stored on a storage module of the telecommunications device,

wherein when the telecommunications device subsequently initiates a network re-attachment procedure and a temporary module identification information is identified to be present on the subscriber identity module, the temporary module identification information from the subscriber identity module is validated against the temporary module identification information authenticator and the identifier of the telecommunications device,

wherein responsive to a positive validation the telecommunications device attempts to attach to the network using the temporary module identification information, and

wherein responsive to a negative validation the telecommunications device attempts to attach to the network using the module identification information.

20. The method of claim 19 , wherein the temporary module identification information comprises a Temporary Mobile Subscriber Identity “TMSI” or a Globally Unique Temporary UE Identity “GUTI”.

21. The method of claim 1 , wherein the module identification information is stored in a cache of the telecommunications device after having been read only once on insertion of the subscriber identity module or on boot up of the telecommunications device,

wherein when the modem reads the module identification information the modem reads the module identification information from the cache, and

wherein when the telecommunications device performs a network attachment procedure the telecommunications device uses the cached module identification information to retrieve the module identification information for the network attachment procedure.

22. At least one non-transitory, computer-readable medium storing a computer program to control a device to perform the method of claim 1 .

23. A device comprising:

processing circuitry to perform data processing; and

non-transitory data storage storing at least one computer program for controlling the processing circuitry to perform the method of claim 1 .