Security

Step 1: Application asks CSE module to verify
MAC of stored mileage (using key #x)
Step 2: CSE module reads mileage and MAC.
CSE module uses key #x to calculates MAC.
CSE module compares both MACs. If identical:
CSE module sets bit in host interface.
Step 3: Application checks bit and asks other
ECUs for mileage (via secure communication).
If bit is set and other ECUs reports same
mileage: stored mileage is ok.
Step 4: ECU gets new mileage. Application
asks CSE module to generate MAC of new
mileage (using key #x).
Step 5: CSE module reads new mileage. CSE
module uses key #x to calculates MAC. CSE
module writes MAC to system RAM.
Step 6: Host writes new mileage and its MAC
into flash. Host sends new mileage to other
nodes (secure communication)
• MAC protects mileage against modification.
• Distributing mileage on other ECUs protects against replay-attacks (i.e., overwriting mileage and MAC with read old
mileage and its MAC).
TM
2d
MAC
Random
number
generator
Bus master
Flash
Stored mileage + MAC
14
2c
2a
MPC5646C
CSE module
Unique ID
AES-128
3b
2a
5a
5c
5a
3a
mileage
Keys
Key #x
Host Interface
5c
System RAM
Calculated MAC
Bit for valid
New mileage
MAC
MPC5646C
Other
CSE module ECUs
Flash
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2b
2e