# The Spectral Image

## The Spetral Image - Incognito 6.0 CTF

| Info     | Details          |
| -------- | ---------------- |
| Category | Digial Forensics |
| Points   | 100              |

## Challenge Overview

> This challenge is called **The Spetral Image b6414**. From the title, we assume that Base64 and ROT14 might be involved.

![](https://3350216265-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F8aLNxke1qPtepwlrf6VI%2Fuploads%2FO4gV6rH40esLO45HKOz6%2Foverview.png?alt=media\&token=96003f92-30b9-4606-a971-0d8ffcfc6727)

When downloading the provided file, we get a `.jpg` file. But after analyzing it, we realize that it's not actually an image — it's an **audio file** disguised as a JPEG.

<figure><img src="https://3350216265-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F8aLNxke1qPtepwlrf6VI%2Fuploads%2F4NyjCWU19S56cMb04yZj%2FScreenshot_1.png?alt=media&#x26;token=ed22d2d9-3713-4ef7-bab0-ccd6653e9236" alt=""><figcaption><p>not a jpg file</p></figcaption></figure>

After converting it to `.wav`, we end up with a **1:50 minute** audio file. Given the challenge's theme, it feels like a transmission of some kind.

A bit of research shows that **1 minute and 50 seconds** is exactly the duration of a **Scottie DX SSTV** transmission — a slow-scan TV format.

### Decoding the SSTV

Using the **RX-SSTV** tool and playing the `.wav` file, we’re able to decode the SSTV signal into an image.

> *Note: To do this, we need to make sure our system audio is routed properly. That means enabling `Stereo Mix` or using a virtual audio driver like **VB-CABLE**. Other loopback tools can work as well.*

The output from RX-SSTV gives us a encoded **string**.

<figure><img src="https://3350216265-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F8aLNxke1qPtepwlrf6VI%2Fuploads%2FHxIrYsAHtVmQQT7QmICv%2Ftwzt.png?alt=media&#x26;token=1b2c7434-ded6-409b-b9eb-2781992aa122" alt="" width="375"><figcaption><p>encoded with b64 and rot14</p></figcaption></figure>

### Decoding the Final String

Given the challenge title contains `b6414`, we try decoding the output using **Base64**, and then applying a **ROT14** cipher to the result.

This gives us the final flag.

<figure><img src="https://3350216265-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F8aLNxke1qPtepwlrf6VI%2Fuploads%2FjdO5u0Y7UhdgkzJ089o6%2Fdecoding.png?alt=media&#x26;token=f9a4abda-61f7-4a69-b020-bd5a0d3cd5f2" alt=""><figcaption><p>decoded with b64, rot14</p></figcaption></figure>

## Final Flag

`ictf{f1y_m3_t0_th3_m00n}`

*made by k0d*
