Doing it for yourself

Last updated on 2025-10-29 | Edit this page

Overview

Questions

  • Can you apply what you’ve learned?

Objectives

  • Develop a signature.
  • Create a signature file.
  • Test the signature file against the workshop test files!

Doing it for yourself

Now that you’ve seen everything there is to know about writing file format signatures and plugging them in, it is time to write one!

If you are doing this in a workshop environment, follow this thread. If you are following along at home in a tutorial, then skip to the small exercise below to find a task that you can complete at home.

Workshop exercise

  1. Split into groups.
  2. Work together to create a signature.
  3. Plug it into DROID/Siegfried
  4. Good luck!
Callout

You can do it!

Many of us have been developing file format signatures for years now and so if you’re new to this you will likely have questions. Your mentor’s should be around and available to help guide your efforts. There will also be an opportunity at the end to discuss how things went.

Discussion

Quite ok!

Your task is to find an identification for the Quite OK Image format. Below you will find a specification and some sample files. Take a look at these in any order you wish to determine what may provde to be a good file format signature for this new file format!

Specification

QOI Sample files

Wrapping up

If you have managed to successfully match QOI files using your own signature file, then start to make some notes about what you did. Think about what worked? What didn’t work? What questions you still have? And anything else that might be relevant. We will revisit this next section!

Local exercise

The following challenge is simply to try and write a DROID compatible signature file that can be used to identify three byte sequences designed for this tutorial. There are sample files available, and all you have to do is match all three!

Challenge

Develop a signature for the following and test it in DROID or Siegfried

56 45 52 53 49 00 4E 00 00 00 00 00 00 00 43 48 41 52 53 45 54 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 43 4F 4C 55 4D 4E 53

56 45 52 53 49 00 4E 00 00 00 00 00 00 00 43 48 41 52 53 45 54 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 43 4F 4C 55 4D 4E 53

56 45 52 53 49 00 4E 00 00 00 00 00 00 00 43 48 41 52 53 45 54 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 43 4F 4C 55 4D 4E 53

Sample files

A solution will appear here shortly.

Callout

Taking note of the extension

You can also record a file format extension in a signature file. If you correctly match the file format extension then tools like Siegfried and DROID will highlight that the file has the correct extension and if a file presents with the incorrect extension they will often warn about that as well.

Wrapping up!

If you have managed to identify the three sample files using your own signature file, congratulations!

If you’re still wrestling with it, take a look at the solution and see if you can plug it into Siegfried and make it work. Take note of how the solution works or how you think it works and have a think about what wasn’t quite working in your own answer.

We’ll wrap up in the next lesson.


Key Points
  • You’ve all the tools needed to write file format signatures.
  • It might not always work.
  • It will certainly take trial and error.
  • Persevere and keep working on it.
  • Practice makes perfect!