> For the complete documentation index, see [llms.txt](https://www.kryptor.co.uk/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.kryptor.co.uk/tutorial/signing-options.md).

# Signing options

## Specifying a custom signature file

If you want to give the signature file a custom name or store it in a different location to the file being signed, you must specify a custom file name/path.

Here's an example:

```bash
$ kryptor -s -t "C:\Users\samuel-lucas6\Documents\file.signature" file.zip
```

## Specifying a comment

This is useful for adding instructions or metadata like an intended file name, timestamps, or version numbers.

Kryptor will verify the comment as part of the signature and display it to the user verifying the signature if verification succeeds. If you don't specify a comment, the default comment will be used.

Remember to type "speech marks" around the comment like so:

```bash
$ kryptor -s -c "Signed by Bob on the 4th of February 2022." file.zip
```

If you don't want the default comment, you can type a space as the comment:

```bash
$ kryptor -s -c " " file.zip
```

## Signing large files

If you have limited RAM, you may not be able to sign large files without prehashing. However, Kryptor automatically uses prehashing when you select a file that's equal to or greater than 1 GiB in size, so this shouldn't be a problem on most machines.

Here's an example:

```bash
$ kryptor -s -l photos.zip
```


---

# 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://www.kryptor.co.uk/tutorial/signing-options.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.