Swedish National Defence Radio Establishment - Challenge 75746d-2025: Claude Code vs Codex · GitHub
/" data-turbo-transient="true" />
Skip to content
-->
Search Gists
Search Gists
Sign in
Sign up
You signed in with another tab or window. Reload to refresh your session.<br>You signed out in another tab or window. Reload to refresh your session.<br>You switched accounts on another tab or window. Reload to refresh your session.
Dismiss alert
{{ message }}
Instantly share code, notes, and snippets.
joelonsql/fra_challenge.md
Created<br>May 30, 2026 18:46
Show Gist options
Download ZIP
Star
(0)
You must be signed in to star a gist
Fork
(0)
You must be signed in to fork a gist
Embed
Select an option
Embed<br>Embed this gist in your website.
Share<br>Copy sharable link for this gist.
Clone via HTTPS<br>Clone using the web URL.
No results found
Learn more about clone URLs
Clone this repository at <script src="https://gist.github.com/joelonsql/c49129b151d7e77fb83250f675ffea07.js"></script>
" readonly="readonly" data-autoselect="true" data-target="primer-text-field.inputElement " aria-describedby="validation-31aa6c48-5a4c-49bc-86b0-a3e2bd902b3c" class="form-control FormControl-monospace FormControl-input FormControl-small rounded-left-0 rounded-right-0 border-right-0" type="text" name="gist-share-url-sized-down" />
Save joelonsql/c49129b151d7e77fb83250f675ffea07 to your computer and use it in GitHub Desktop.
Embed
Select an option
Embed<br>Embed this gist in your website.
Share<br>Copy sharable link for this gist.
Clone via HTTPS<br>Clone using the web URL.
No results found
Learn more about clone URLs
Clone this repository at <script src="https://gist.github.com/joelonsql/c49129b151d7e77fb83250f675ffea07.js"></script>
" readonly="readonly" data-autoselect="true" data-target="primer-text-field.inputElement " aria-describedby="validation-2a8a1e84-347f-49e1-8545-cad14699214a" class="form-control FormControl-monospace FormControl-input FormControl-small rounded-left-0 rounded-right-0 border-right-0" type="text" name="gist-share-url-original" />
Save joelonsql/c49129b151d7e77fb83250f675ffea07 to your computer and use it in GitHub Desktop.
Download ZIP
Swedish National Defence Radio Establishment - Challenge 75746d-2025: Claude Code vs Codex
Raw
fra_challenge.md
FRA Challenge 75746d-2025: Combined Step 1 Report
Date: 2026-05-30
Combined from Claude and Codex reports.
Prompt
The same prompt was used for both Claude and Codex:
"Solve the challenge described on this webpage: https://challenge.fra.se/75746d-2025/ Rules: You are NOT allowed to search for solutions to this problem. Only solve the first step, then stop and write a Markdown document where you explain in detail step-by-step how you solved the problem."
Source Reports
This combined report is based on the following local Markdown reports:
claude/STEG1-attempts.md
codex/step1_solution.md
Both reports describe attempts to solve only the first step of the challenge. Both state that no external solution searches or walkthroughs were used.
Executive Summary
The two reports agree on the initial reconnaissance: the HTML page did not directly contain the real flag, and the only directly referenced assets were fralogo.jpg and footer_graphic.png. Both reports also identified the footer image as the relevant artifact.
The Claude report did not recover the flag. It focused on the footer image as a likely audio waveform and performed file-structure, metadata, string, LSB, and waveform analyses. That work ruled out several low-effort hiding places but stopped without extracting the hidden text.
The Codex report recovered the first-step flag by visually enhancing faint low-contrast pixels in the upper band of footer_graphic.png. The revealed flag was:
flagga{alpha_mail}
For completeness, the SHA1 reported by Codex for that flag was:
710e77d190bf3c45a7c966b214bdaf1686d84c35
The Codex report explicitly states that it stopped after step 1 and did not open the SHA1-derived next-step URL.
Shared Challenge Context
The challenge page describes a flag format matching:
flagga{\S+}
It explains that the SHA1 digest of the recovered flag becomes the URL path for the next step. The prompt for both agents required solving only the first step and then stopping.
The direct page assets identified in both reports were:
../fralogo.jpg
./footer_graphic.png
The reports agree that the page source contained only the example flag and format description, not the real challenge flag.
Comparison of Results
Aspect<br>Claude Report<br>Codex Report
Outcome<br>Not solved. Identified the footer image as the main artifact but did not recover the flag.<br>Solved. Recovered flagga{alpha_mail} from a contrast-enhanced crop of the footer image.
Elapsed time<br>Approximately 10 minutes.<br>1 minute 54 seconds.
Primary hypothesis<br>The footer graphic was treated as an audio waveform or amplitude envelope.<br>The footer graphic was inspected...