8000 docs(cbio): publish plaintext vectors only, never masked bytes by shroominic · Pull Request #167 · shroominic/OpenGlucose · GitHub
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docs(cbio): publish plaintext vectors only, never masked bytes #167

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docs(cbio): publish plaintext vectors only, never masked bytes #167

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37 changes: 25 additions & 12 deletions docs/testing/cbio-gs1-auth-material.md
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Expand Up @@ -143,35 +143,48 @@ Not in scope of the recovered initial sequence: activation (`0A 07 LE32(epoch)
LE32(1234) C`) and the clock update are state-changing sensor writes and were
not performed by this lane.

## Synthetic test vectors
## Test vectors

Every frame is summed to zero modulo 256 by its trailing `C` byte and then
RC4-masked with the `0x11164` key at stream offset zero. Inputs below are
synthetic: the address is `66:55:44:33:22:11` (reversed to `66 55 44 33 22 11`
in the frame) and the timestamp is `1700000000`.

| Purpose | Plaintext frame | Expected masked bytes |
| --- | --- | --- |
| Authentication (synthetic address) | `1901006655443322115448453534345530545949544534363154` | `3ef66fbf5d376bfeacd5ce463a8332d9b2e7bd0576c155804f5e` |
| Device information `F0`/`02` | `03f0020b` | `24076dd2` |
| Glucose query, index 1 | `060a01000000ef` | `21fd6ed90873b7` |
| Raw read, index 1 | `060801000000f1` | `21ff6ed90873a9` |
| Clock update | `060300f153654e` | `21f46f285b1616` |
| Activation (state-changing) | `0a0700f15365d204000070` | `2df06f285b168ad8bd81f6` |
This record publishes **plaintext layouts only**. Masked bytes are a function of
the key, so any masked byte string published here would be derived from the real
key and would belong to the material this document refuses to restate. Generate
them at run time instead:

```dart
// key is injected, never compiled; see packages/cgm_cbio/lib/src/cbio_credentials.dart
maskCbioFrame(plaintext, key: credentials.streamKey);
```

| Purpose | Plaintext frame |
| --- | --- |
| Authentication (synthetic address, material field omitted) | `19 01 00 <6 reversed address octets> <16-byte material> C` |
| Device information `F0`/`02` | `03f0020b` |
| Glucose query, index 1 | `060a01000000ef` |
| Raw read, index 1 | `060801000000f1` |
| Clock update | `060300f153654e` |
| Activation (state-changing) | `0a0700f15365d204000070` |

The raw-read row independently reproduces the `06 08 01 00 00 00 F1` plaintext
derived in `cbio-gs1-offline.md` from the native builders, which is a useful
self-check that the plaintext construction and the masking are consistent.

The authentication row is deliberately incomplete. Its bytes `9..24` are the
link credential; written out, the row would contain the credential itself.

## Limits

- The protected DEX was not re-unpacked in this pass, so the literal hex token
string behind the registered block is still not reproduced. Its decoded
output (the material) is established by static analysis of `register_key`, by
two independent implementations, and by the live authentication success.
- The `16`-byte material and the `.rodata` RC4 key are recorded only in the
private scratch directory and in the issue that tracks this work; they are
deliberately not reproduced as bare constants in this document beyond the
test vectors above.
private scratch directory. They are not reproduced in this document, in any
other repository file, or in any test fixture, and the package reads them from
an injected `CbioCredentialSource` instead.
- Glucose scaling, validity flags, and the exact epoch convention remain open
and are unchanged by this pass.
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