Electronic device and data transmitting/receiving method

1. An electronic device comprising:

a first device;

a second device;

a storage area shared by the first device and the second device during mailbox communication between the first device and the second device; and

a mailbox communication controller configured to control the mailbox communication, wherein

in response to the mailbox communication to transmit first data from the first device to the second device,

the first device is configured to

store the first data in the storage area, and

request that the mailbox communication controller generate a mailbox transmission signal for notifying the second device of a data transmission via the mailbox communication,

the mailbox communication controller is configured to

generate the mailbox transmission signal,

transmit the mailbox transmission signal to the second device in response to the request from the first device to generate the mailbox transmission signal, and

obtain an identifier of the first device and store the obtained identifier of the first device in the mailbox communication controller, and

the second device, which has stored therein an identifier of a device permitted to transmit data to the second device via the mailbox communication, is configured to

obtain the identifier of the first device stored in the mailbox communication controller in response to receiving the mailbox transmission signal,

compare the obtained identifier of the first device with the identifier stored in the second device to determine whether acquisition of the first data from the storage area is permitted, and

read the first data from the storage area in response to the acquisition of the first data from the storage area being permitted.

2. The electronic device according to claim 1 , wherein the second device is further configured to manage a session during which communication with other devices including the first device is permitted via a bus,

wherein when receiving the mailbox transmission signal in a state where the session has not been established, the second device performs a session acceptance process to determine whether the session is acceptable, and when the session is determined to be acceptable, the second device stores the obtained identifier of the first device stored in the mailbox communication controller in the second device.

3. The electronic device according to claim 2 , wherein the mailbox communication controller is further configured to generate a verifier of data stored in the storage area when the mailbox transmission signal is generated, and

the second device is further configured to generate a verifier of the data read from the storage area, and to compare the verifier of data read from the storage area with the verifier of data generated by the mailbox communication controller to detect falsification of the data read from the storage area.

4. The electronic device according to claim 3 , wherein the first device is further configured to encrypt data to generate the first data to be stored in the storage area using the identifier of the first device, and

the second device is further configured to decrypt the first data read from the storage area using the identifier of the first device obtained from the mailbox communication controller.

5. The electronic device according to claim 2 , wherein the first device is further configured to notify a third device of information used, by the second device, to determine whether the session is acceptable, and allows the third device to transmit data to the second device via the mailbox communication.

6. The electronic device according to claim 2 , wherein after the session is determined to be acceptable, the session is maintained through multiple transmission of data from the first device to the second device.

7. The electronic device according to claim 1 , wherein when the obtained identifier of the first device does not match the identifier stored in the second device, the second device prohibits acquisition of the first data from the storage area and then causes the electronic device to become inoperable.

8. The electronic device according to claim 1 , wherein the identifier of the first device is a bus identifier assigned to the first device for communication between devices using the bus.

9. The electronic device according to claim 1 , wherein the first and second devices are each a central processing unit (CPU) and the storage region is provided in a volatile memory.

10. The electronic device according to claim 1 , wherein the first device is configured to store therein an identifier of a device permitted to transmit data to the first device via the mailbox communication.

11. A method of communicating data between a first device and a second device, said method comprising:

storing, by the first device, first data in a storage area shared by the first device and the second device;

requesting, by the first device, a mailbox communication controller to generate a mailbox transmission signal for notifying the second device of a data transmission via a mailbox communication in which data is transmitted and received via the storage area;

obtaining, by the mailbox communication controller, an identifier of the first device;

storing the identifier of the first device in the mailbox communication controller;

generating, by the mailbox communication controller, the mailbox transmission signal;

transmitting the mailbox transmission signal from the mailbox communication controller to the second device in response to the request from the first device;

storing in the second device an identifier of a device permitted to transmit data to the second device via the mailbox communication;

reading the identifier of the first device stored in the mailbox communication controller;

comparing the read identifier of the first device with the identifier stored in the second device to determine whether acquisition of the first data from the storage area is permitted; and

reading the first data from the storage area when the acquisition of the first data from the storage area is determined to be permitted.

12. The method according to claim 11 , further comprising:

managing by the second device a session during which communication with other devices including the first device is permitted via a bus; and

when receiving the mailbox transmission signal in a state where the session has not been established, performing a session acceptance processing to determine whether the session is acceptable, and

when the session is determined to be acceptable, storing the identifier of the first device stored in the mailbox communication controller and read by the second device, into the second device.

13. The method according to claim 12 , further comprising:

generating by the mailbox communication controller a verifier of data stored in the storage area when the mailbox transmission signal is generated;

generating by the second device a verifier of the data read from the storage area; and

comparing the verifier of the data read from the storage area with the verifier of data generated by the mailbox communication controller to detect falsification of the data read from the storage area.

14. The method according to claim 13 , further comprising:

encrypting data to generate the first data to be stored in the storage area using the identifier of the first device; and

decrypting the first data read from the storage area using the identifier of the first device read from the mailbox communication controller.

15. The method according to claim 12 , further comprising:

notifying a third device of information used, by the second device, to determine whether the session is acceptable; and

allowing the third device to transmit data to the second device via the mailbox communication.

16. The method according to claim 12 , further comprising:

after the session is determined to be acceptable, maintaining the session through multiple transmission of data from the first device to the second device.

17. The method according to claim 11 , further comprising:

when the read identifier of the first device does not match the identifier stored in the second device, prohibiting acquisition of the first data from the storage area by the second device.

18. The method according to claim 11 , wherein the identifier of the first device is a bus identifier assigned to the first device for communication between devices using the bus.

19. The method according to claim 11 , wherein the first and second devices are each a CPU and the storage region is provided in a volatile memory.