METHOD FOR AUTHENTICATING A PROGRAM AND CORRESPONDING INTEGRATED CIRCUIT

• US 20200134164A1
• Filed: 10/22/2019
• Published: 04/30/2020
• Est. Priority Date: 10/26/2018
• Status: Active Grant

• Current Assignee: STMicroelectronics Grand Ouest SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Grand Ouest SAS (STMicroelectronics NV)
• Inventors: BERTHELOT, Vincent, DAINECHE, Layachi
• Granted Patent: US 11,269,986 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 21/44 Program or device authentication
• CPC Class Codes: G06F 21/51 at application loading time, e.g. accepting, rejecting, starting or inhibiting executable software based on integrity or source reliability
• CPC Class Codes: G06F 21/52 during program execution, e.g. stack integrity ; Preventing unwanted data erasure; Buffer overflow

Abstract

A memory stores a program to be executed by a microprocessor. The program includes a first program part and a second program part. An authenticator is configured to authenticate the program and includes a module that is external to the microprocessor and configured to authenticate said first program part when the microprocessor is inactive. The authenticator further activates the microprocessor to execute the first program part and authenticate said second program part using instructions of the first program part if the module has authenticated the first program part. The microprocessor then executes the second program part if the microprocessor has authenticated said second program part.

Claims

1. A method for authenticating a program stored in a memory, said program configured to be executed by a microprocessor and including a first program part and a second program part, the method including:

performing a first authentication of said first program part by a module situated outside said microprocessor with the microprocessor being in an inactive mode;

if the first program part is authenticated by said module, activating said microprocessor to execute said first program part, including performing a second authentication of said second program part; and

if the second part is authenticated, executing said second program part by the activated microprocessor.

2. The method according to claim 1, comprising, prior to performing the first authentication, storing in said module of a first identifier of the first program part, and wherein performing the first authentication includes:

computing a first new identifier of the first program part;

comparing the first identifier to the first new identifier; and

authenticating the first program part if the first identifier and the first new identifier are identical.

3. The method according to claim 2, wherein computing the first new identifier comprises implementing a first hash function having said first program part as input parameter and delivering said first new identifier as output.

4. The method according to claim 1, further comprising, prior to performing the first authentication, storing in the second program part of a second identifier of the second program part, and wherein performing the second authentication comprises:

computing a second new identifier of the second program part;

comparing the second identifier to the second new identifier; and

authenticating the second program part if the second identifier and the second new identifier are identical.

5. The method according to claim 4, wherein computing the second new identifier comprises implementing a second hash function having said second program part and a key as input parameters and delivering said second new identifier as output.

6. The method according to claim 5, wherein said key is stored in a protected module and further comprising:

permitting access to the key only in response to execution of said first program part by the activated microprocessor; and

blocking access to said key in the protected module once the second program part has been authenticated.

7. The method according to claim 6, wherein performing the first authentication occurs in response to a system boot, and wherein blocking access to said key comprises blocking access to the protected module wherein the key is stored until a next system boot occurs.

8. The method according to claim 6, further comprising restricting access to the key to only the activated microprocessor.

9. A system, comprising:

a microprocessor;

a memory configured to store a program to be executed by the microprocessor and comprising a first program part and a second program part; and

an authentication circuit configured to authenticate the program, said authentication circuit comprising;

a module external to the microprocessor and configured to authenticate said first program part while the microprocessor is in an inactive mode; and

if the first program part is authenticated, then configuring the microprocessor an active mode so as to execute said first program part and authenticate said second program part using instructions of the first program part;

if the second program part is authenticated, then configuring the microprocessor to execute the second program part.

10. The system according to claim 9, wherein said module stores a first identifier of the first program part determined prior to the authentication of the first program part, said module further configured to perform a first computation of a first new identifier of the first program part and compare the first identifier to the first new identifier, the first program part being considered to be authenticated by said module if the first identifier and the first new identifier are identical.

11. The system according to claim 10, wherein the first computation comprises implementation of a first hash function having said first program part as an input parameter and delivering the first new identifier as output.

12. The system according to claim 10, wherein the second program part comprises a second identifier, the microprocessor being configured so as to perform a second computation of a second new identifier and compare the second identifier with the second new identifier, the second program part being considered to be authenticated by the microprocessor if the second identifier and the second new identifier are identical.

13. The system according to claim 12, wherein the second computation comprises implementation of a second hash function having said second program part and a key as input parameters and delivering the second new identifier as output.

14. The system according to claim 13, further comprising a protected module configured to store said key in a manner where the stored key is accessible only in response to execution of said first program part by the activated microprocessor, the microprocessor being further configured to blocking access to said key in the protected module once the second program part has been authenticated.

15. The system according to claim 14, wherein said module performs the first authentication in response to a system boot, and wherein the microprocessor blocks access to the protected module wherein the key is stored until a next system boot occurs.

16. The system according to claim 14, wherein the protected module is configured to restrict access to the key to only the activated microprocessor.