Method for locking a rewritable non-volatile memory and electronic device implementing said method

1 . A method for locking a rewritable non-volatile memory of an electronic device, the method comprising:

performing a first step of initialising the electronic device;

selecting at least one memory area of the rewritable non-volatile memory from a set of N memory areas of the rewritable non-volatile memory, each of the N memory areas comprising a version of a content, N being an integer ≥2,

wherein the selecting at least one memory area comprises:

comparing the versions of the content stored in the N memory areas;

selecting a memory area comprising a most recent version of the content; and when each of M memory areas, where M is an integer belonging to [2; N], comprise the same most recent version of the content, selecting, from said M memory areas, a memory area different from a memory area identified as having been selected during a previous initialization of the electronic device, said previous initialization being associated with a booting or rebooting of the electronic device;

locking the at least one selected memory area by a locking known as volatile locking, the locking being deactivated only by powering down the at least one selected memory area;

wherein at least one non-selected memory area of the N memory areas remains unlocked and is configured for receiving a new version of the content for a subsequent update; and

performing a second step of initialising the electronic device using a content stored in the at least one selected memory area.

2 . The method according to claim 1 , furthermore comprising hardware maintenance of the N memory areas before any locking of the at least one selected memory area, the hardware maintenance comprising an error detection and a correction of errors detected.

3 . The method according to claim 1 , wherein the performing a first step of initialising the electronic device comprises:

authenticating, by a secure initial boot, first booting software stored in a first memory area of the rewritable non-volatile memory;

starting up the first booting software;

authenticating, by the first booting software, second booting software stored in a second memory area of the rewritable non-volatile memory different from the first area;

starting up the second booting software; and

authenticating, by the second booting software, for each of the N memory areas, the content.

4 . The method according to claim 3 , wherein locking the at least one selected memory area by volatile locking furthermore comprises locking the second memory area by volatile locking.

5 . The method according to claim 4 , furthermore comprising hardware maintenance of the second memory area before any volatile locking of the second memory area, the hardware maintenance comprising an error detection and a correction of errors detected.

6 . The method according to claim 3 , wherein the first memory area is a one-time programming memory.

7 . The method according to claim 1 , wherein the rewritable non-volatile memory area is a NAND flash memory and/or an eMMC memory.

8 . The method according to claim 1 , wherein the content is application firmware and the second step of initialising the electronic device comprises the starting up of the application firmware.

9 . The method according to claim 1 , furthermore comprising, after the performing the second step of initialising the electronic device using the content stored in the at least one selected memory area:

determining that an update is necessary;

selecting from the set of N memory areas at least one non-locked memory area;

loading a new version of the content into the at least one non-locked memory area selected;

rebooting the electronic device.

10 . An electronic device comprising a rewritable non-volatile memory and at least one processor configured for:

performing a first step of initialising the electronic device;

selecting at least one memory area of the rewritable non-volatile memory from a set of N memory areas of the rewritable non-volatile memory, each of the N memory areas comprising a content, N being an integer ≥2,

wherein the selecting at least one memory area comprises:

comparing the versions of the content stored in the N memory areas;

selecting a memory area comprising a most recent version of the content; and

when each of M memory areas, where M is an integer belonging to [2; N], comprise the same most recent version of the content, selecting, from said M memory areas, a memory area different from a memory area identified as having been selected during a previous initialization of the electronic device, said previous initialization being associated with a booting or rebooting of the electronic device,

locking the at least one selected memory area by a locking, known as volatile locking, the locking being deactivated only by powering down the at least one selected memory area; and

wherein at least one non-selected memory area remains unlocked and is configured for receiving a new version of the content for a subsequent update; and

performing a second step of initialising the electronic device using a content stored in the at least one selected memory area.

11 . A non-transitory computer-readable storage medium that stores a computer program comprising instructions for implementing the locking method according to claim 1 , when the program is executed by a processor.