Seed and Key concept
Seed and key algorithm to limit the tool access for authorized users. This algorithm can be developed and used in different ways, its specific to the tool manufacturer. The ECU send/request the seed the diagnostic tool, then tool receive the seed. The tool apply the secrete algorithm to find the key and send it back to ECU. Mean time ECU will calculate the key by using same kind of algorithm. ECU starts to compare these two keys. If it matches the ECU will be unlocked with corresponding diagnostic tool.