Method and system for securely updating firmware in a computing device
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.
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.