> For the complete documentation index, see [llms.txt](https://docs.verifone.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.verifone.com/kld/key-information/key-import/how-to-import-key-files-through-usb.md).

# How to Import Key Files through USB

* Read **Key Lists** and the difference between **Keys** and **Key Lists**.
  * See [Key Concepts](/kld/kld-user-guide/user-guide-p400/key-concepts.md).
* Don’t skip [Handling Key Import Error](#handling-key-import-error).
* Key import follows a fixed USB directory structure.
* Key import also expects specific folder and file names.

### USB directory and file structure

* Folder names `BDK`, `FIXED`, `MS/KEK`,  `MS/KBPK`, and `IK` are fixed.
* These folders are optional if you have no keys for them.
* File names `fixed-key.txt` and `dukpt-bdk.txt` are fixed.
* Under `MS` and `IK`, file names are flexible.
* Under `MS` and `IK`, the number of files is flexible.
* The directory names and structure are not flexible.

<figure><img src="/files/JP9TvYytkHaPhymOQ6K3" alt=""><figcaption></figcaption></figure>

### File naming concept

* Under `MS` and `IK`, you can use many files.
* See the **File naming concept** in:
  * [TR-31 File Formats (per folder / key type)](/kld/key-information/key-import.md#tr-31-file-formats-per-folder-key-type)

### Handling Key Import Error

This is covered in detail in:

* [Handling Key Import Error](/kld/key-information/key-import/handling-key-import-error.md)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.verifone.com/kld/key-information/key-import/how-to-import-key-files-through-usb.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.