Method and system for securely updating firmware in a computing device

• US 9,792,439 B2
• Filed: 09/19/2012
• Issued: 10/17/2017
• Est. Priority Date: 09/19/2012
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Colnot, Vincent Cedric
• Primary Examiner(s): Desrosiers, Evans
• Application Number:
  US13/622,534
• Publication Number:
  US 20140082373A1
• Time in Patent Office: 1,854 Days
• Field of Search: 713193, 713168-174, 713182-186, 713202, 709206, 709225, 709229, 709249, 709389, 726 2- 8
• CPC Class Codes: G06F 21/572 Secure firmware programming, e.g. of basic input output system [BIOS]
• CPC Class Codes: G06F 21/575 Secure boot

Abstract

Embodiments of a method are disclosed. One embodiment is a method for securely updating firmware in a computing device, in which the computing device includes a host processor and a non-volatile memory. The method involves receiving a double-encrypted firmware image from an external firmware source, wherein the double-encrypted firmware image is generated from firmware that is encrypted a first time using a first crypto-key and then encrypted a second time using a second crypto-key. The method also involves receiving the second crypto-key from an external key source, decrypting the double-encrypted firmware image using the second crypto-key to produce an encrypted firmware image, storing the encrypted firmware image in the non-volatile memory of the computing device, reading the encrypted firmware image from the non-volatile memory of the computing device, decrypting the encrypted firmware image using the first crypto-key, and executing the firmware on the computing device.

Claims

1. A method for updating firmware in a computing device, the computing device including a host processor and a non-volatile memory, the method comprising:

receiving a double-encrypted firmware image from an external firmware source, wherein the double-encrypted firmware image is generated from firmware that is encrypted a first time using a first crypto-key and then encrypted a second time using a second crypto-key;

receiving the second crypto-key from an external key source;

decrypting the double-encrypted firmware image using the second crypto-key to produce an encrypted firmware image;

storing the encrypted firmware image in the non-volatile memory of the computing device;

reading the encrypted firmware image from the non-volatile memory of the computing device;

decrypting the encrypted firmware image using the first crypto-key to produce the firmware; and

executing the firmware on the computing device;

wherein the second crypto-key is received and stored at a secure element located between the host processor and the non-volatile memory; and

wherein the secure element is configured to apply decryption to data addressed to code blocks in the non-volatile memory and to pass without decryption data addressed to data blocks in the non-volatile memory.

2. The method of claim 1 wherein the double-encrypted firmware image is decrypted by the secure element using the second crypto-key.

3. The method of claim 2 wherein the secure element includes a host-side interface connected to a host-side data bus and a memory-side interface connected to a memory-side data bus, and wherein the secure element includes a crypto-engine configured to decrypt the double-encrypted firmware.

4. The method of claim 1 wherein the double-encrypted firmware image is decrypted using the second crypto-key upon receipt of the double-encrypted firmware image from the external firmware source without first being stored in the non-volatile memory.

5. The method of claim 1 wherein the double-encrypted firmware image is first stored in the non-volatile memory and then read from the non-volatile memory and decrypted using the second crypto-key.

6. The method of claim 1 wherein the first crypto-key is a group key (GK1), which is the same for a group of computing devices, and wherein the second crypto-key is a group key (GK2), which is the same for a particular version of the firmware.

7. The method of claim 1 wherein the second crypto-key is received from the external key source via a secure channel.

8. The method of claim 1 further comprising decrypting an encrypted random number at the secure element to confirm the presence of the secure element.

9. A computing device comprising:

a data interface configured to receive a double-encrypted firmware image from an external firmware source, wherein the double-encrypted firmware image is generated from firmware that is encrypted a first time using a first crypto-key and then encrypted a second time using a second crypto-key, and to receive the second crypto-key from an external key source;

a host processor configured to execute program code of the firmware;

a non-volatile memory configured to store an encrypted image of the firmware; and

a secure element located in a data path between the host processor and the non-volatile memory and having a crypto-engine, the crypto-engine being configured to decrypt the double-encrypted firmware image using the second crypto-key to produce an encrypted firmware image and the secure element being configured to provide the encrypted firmware image to the non-volatile memory of the computing device for storage;

the host processor being configured to read the encrypted firmware image from the non-volatile memory, to decrypt the encrypted firmware image using the first crypto-key to produce the firmware, and to execute program code of the firmware on the computing device;

wherein the secure element is configured to apply decryption to data addressed to code blocks in the non-volatile memory and to pass without decryption data addressed to data blocks in the non-volatile memory.

10. The computing system of claim 9 wherein the double-encrypted firmware image is decrypted at the secure element using the second crypto-key upon receipt of the double-encrypted firmware image from the external firmware source without first being stored in the non-volatile memory.

11. The computing system of claim 9 wherein the double-encrypted firmware image is first passed through the secure element and stored in the non-volatile memory without being decrypted and then read from the non-volatile memory upon boot up and decrypted at the secure element using the second crypto-key.

12. The computing system of claim 9 wherein the first crypto-key is a device group key (GK1), which is the same for a group of computing devices, and wherein the second crypto-key is a group key (GK2), which is the same for a particular version of the firmware.

13. A method for confirming the presence of a secure element in a computing device, the computing device including a host processor and a non-volatile memory, the method comprising:

receiving an encrypted random number at the secure element, wherein the random number is encrypted using a crypto-key;

receiving the crypto-key from an external key source;

decrypting the encrypted random number at the secure element using the crypto-key to produce a decrypted random number;

storing the decrypted random number in the non-volatile memory of the computing device;

reading the decrypted random number from the non-volatile memory of the computing device;

comparing the decrypted random number to a stored version of the random number; and

confirming the presence of the element if the decrypted random number matches the stored random number.

14. The method of claim 13 wherein the crypto-key is received and stored at a secure element, and wherein the secure element is located between the host processor and the non-volatile memory.

15. The method of claim 14 wherein the secure element is configured to apply decryption to data addressed to code blocks in the non-volatile memory and to pass without decryption data addressed to data blocks in the non-volatile memory.

16. The method of claim 13 wherein the crypto-key is a group key (GK), which is the same for a group of computing devices.

17. The method of claim 13 wherein the crypto-key is a session key (SK), which is specific to a communications session of the computing device.