Secure boot of a processing chip
Techniques in electronic systems, such as in systems including a processing chip and one or more external memory chips, provide improvements in one or more of system security (such as intrusion and/or virus/malware prevention), performance, cost, and efficiency. For example, the processing chip includes at least one CPU and circuitry enabling the at least one CPU to securely boot from an external, non-volatile memory chip containing encrypted, executable code. The circuitry comprises immutable hardware to copy the executable code from the non-volatile memory to another external memory from which the at least one CPU is able to access it. The encryption uses a key created at a manufacturing time of and unique to the processing chip that is never CPU-accessible, forming a secure hardware association between the processing chip and the non-volatile memory chip.
1. A method for performing a secure boot of a processing chip, comprising:
holding one or more central processing units (CPUs) of the processing chip in a reset state;
subsequent to boot hardware of the processing chip receiving a reset, copying, by the boot hardware, executable code from an external non-volatile boot storage into an external memory; and
subsequent to the copying, releasing, by the boot hardware, the reset state on at least one of the one or more CPUs, wherein the boot hardware does not contain a run-time-programmable CPU,
wherein the executable code as stored in the external non-volatile boot storage is encrypted using a key that is part of the boot hardware, wherein the key is not accessible by the one or more CPUs, wherein the processing chip is a particular processing chip of multiple processing chips, and the executable code as stored in the external non-volatile boot storage is uniquely decryptable within the particular processing chip.
2. The method of claim 1 , wherein subsequent to a manufacturing time of the processing chip, the boot hardware is immutable hardware.
3. The method of claim 1 , wherein the executable code comprises an operating system.
4. The method of claim 1 , wherein the copying comprises performing an integrity check on the executable code.
5. The method of claim 1 , wherein the reset is received on a reset signal, and
wherein the method further comprises:
beginning the holding of the one or more CPUs in the reset state in response to the reset signal being asserted, and continuing the holding of the one or more CPUs in the reset state until released from the reset state.
6. The method of claim 1 , wherein the external non-volatile boot storage is inaccessible by software executing on the one or more CPUs.
7. The method of claim 1 , wherein the key is a particular key; and
wherein the method further comprises:
creating multiple keys comprising the particular key at a manufacturing time of the particular processing chip using a physically unclonable function that is part of the particular processing chip.
8. The method of claim 7 , wherein the copying by the boot hardware of the executable code from the external non-volatile boot storage into the external memory comprises the boot hardware decrypting the executable code stored in the external non-volatile boot storage with the particular key and re-encrypting the executable code with another one of the multiple keys; and
wherein the copy of the executable code as stored in the external memory is encrypted with the another one of the multiple keys.
9. An integrated circuit, comprising:
one or more central processing units (CPUs);
boot hardware coupled to the one or more CPUs and configured to perform operations comprising:
holding the one or more CPUs in a reset state;
subsequent to receiving a reset, copying executable code from an external non-volatile boot storage into an external memory; and
subsequent to the copying, releasing the reset state on at least one of the one or more CPUs, wherein the boot hardware does not contain a run-time-programmable CPU,
wherein the executable code as stored in the external non-volatile boot storage is encrypted using a key that is part of the boot hardware, wherein the key is not accessible by the one or more CPUs, wherein the processing chip is a particular processing chip of multiple processing chips, and the executable code as stored in the external non-volatile boot storage is uniquely decryptable within the particular processing chip.
10. The integrated circuit of claim 9 , wherein subsequent to a manufacturing time of the integrated circuit, the boot hardware is immutable hardware.
11. The integrated circuit of claim 9 , wherein the boot hardware is independent of the one or more CPUs.
12. The integrated circuit of claim 9 , wherein the executable code comprises an operating system.
13. The integrated circuit of claim 9 , wherein the copying comprises performing an integrity check on the executable code.
14. The integrated circuit of claim 9 , wherein the boot hardware is configured to receive the reset on a reset signal, and
wherein the operations further comprise:
beginning the holding of the one or more CPUs in the reset state in response to the reset signal being asserted, and continuing the holding of the one or more CPUs in the reset state until released from the reset state.
15. The integrated circuit of claim 9 , wherein the external non-volatile boot storage is inaccessible by software executing on the one or more CPUs.
16. The integrated circuit of claim 9 , wherein the key is a particular key; and
wherein the operations further comprise:
creating multiple keys comprising the particular key at a manufacturing time of the particular processing chip using a physically unclonable function that is part of the particular processing chip.