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Introduction.
Explanation of ISO 14229, UDS.
This time, SecurityAccess will be explained.
SecurityAccess Services
Back to the explanation of the various services again.
In turn, I will explain the SecurityAccess service.
From the name, you can probably guess that this is a security-related function.
Let’s start with the message structure.
SecurityAccess Service Request Messages
There are two types of request messages for the SecurityAccess service
- requestSeed
- sendKey
The message structure of requestSeed is as follows.
| Position | Parameter Name | Value |
|---|---|---|
| 1 | SecurityAcces Request SID | 0x27 |
| 2 | sub-function = [ securityAccessType = requestSeed ] | 0x01,0x03,0x05,0x07-0x7D |
The message structure of sendkey is as follows.
| Position | Parameter Name | Value |
|---|---|---|
| 1 | SecurityAcces Request SID | 0x27 |
| 2 | sub-function = [ securityAccessType = sendKey ] | 0x02,0x04,0x06,0x08-0x7E |
| 3-n | securityKey | 0x00 – 0xFF |
You may be confused by the sudden appearance of two different message structures.
The SecurityAccess service has two types of message structures: requestSeed and sendKey.
At first glance, they look similar, but the point is the sub-function.
You will notice that the requestSeed is odd and the sendKey is even.
This is no coincidence; the meaning of the request message switches depending on the odd or even number of sub-functions
Response messages for SecurityAccess service
Naturally, there are two types of response messages.
The response message to requestSeed is as follows.
| Position | Parameter Name | Value |
|---|---|---|
| 1 | SecurityAcces Response SID | 0x67 |
| 2 | sub-function = [ securityAccessType = requestSeed ] | 0x01,0x03,0x05,0x07-0x7D |
| 3-n | securitySeed | 0x00 – 0xFF |
And the response message to sendKey is as follows.
| Position | Parameter Name | Value |
|---|---|---|
| 1 | SecurityAcces Response SID | 0x67 |
| 2 | sub-function = [ securityAccessType = sendKey ] | 0x02,0x04,0x06,0x08-0x7E |
You will see that the words Seed and Key are the key points.
In the next article, I will explain the concept of this service.
Conclusion
- The SecurityAccess service has two major message patterns.
- requestSeed.
- Odd sub-functions.
- sendKey.
- Even sub-functions.
- requestSeed.
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