> For the complete documentation index, see [llms.txt](https://help.security.gallagher.com/knowledge-hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.security.gallagher.com/knowledge-hub/products/cc-hardware/readers/t-series/t-series-encryption-keys-reporting-tam.md).

# HBUS encryption keys report tampered

Resolve HBUS encryption key mismatches after device moves or extended offline periods.

### Symptoms and causes

The keys between HBUS devices (readers and I/O) are generated and updated regularly by the controller they are connected to. These keys, combined with the serial identifier, prevent devices from being surreptitiously switched between controllers or sites.

### Error condition

If these keys are altered, errors appear in the **Status and Overrides tab** of the HBUS device. The HBUS device will not come online due to the encryption mismatch.

![Encryption key mismatch error in the Status and Overrides tab](https://328339335-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F6bM8WhlBE9BYizPWJaPN%2Fuploads%2Fgit-blob-5e232627cdb7b7945292c9c1de288e00260d70a3%2FSECHUB-TSERIES-ENCRYPTION-01-tamper-error.png?alt=media)

### Resolve the encryption mismatch

1. Open the **Connections tab** of the affected HBUS device in Command Centre.
2. Highlight the **Serial** field value and cut it (**Ctrl+X**).
3. Click **Apply** (with the serial field now empty).
4. Paste the serial value back in (**Ctrl+V**).
5. Click **Apply** again.

This reinitialises the HBUS device and regenerates the keys between the Controller and the HBUS item.

### Common causes

1. **Cross-site move without deconfiguration:** An HBUS device is connected to System A, physically removed without deconfiguring it from Command Centre, connected to System B and configured (keys change during this process), then returned to System A and reinstalled without making changes in Command Centre. The keys mismatch and the device will not come online.
2. **Extended offline period:** An HBUS device is configured and online on a system. It is physically removed from the HBUS connection (or disconnected from the controller) and left offline for an **extended period (a week or more)** without being deconfigured in Command Centre. When reconnected to the controller, the encryption mismatch message appears in the Status and Overrides tab.

***

🔗 **Related**

* [T Series - Non HBUS compatible](/knowledge-hub/products/cc-hardware/readers/t-series/t-series-non-hbus-compatible.md). Which readers are HBUS-capable in the first place.
* [T Series](/knowledge-hub/products/cc-hardware/readers/t-series.md). The T Series range.


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