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Hiding in Plain Sight

Challenge​

Content preserved from the original writeup source. Minimal normalization was applied to fit platform format.

Solution​

Original Writeup Content (Preserved)​

Hiding in Plain Sight - Write-Up

Challenge​

A single image file was provided: hello.webp.

Prompt hint:

  • "There's something strange about this image..."
  • Flag format: DawgCTF{Person_Or_Object}

Initial Checks​

I started with basic file and metadata inspection:

  • Confirmed hello.webp is a normal VP8 WebP image (1024x1024).
  • Checked EXIF/metadata with exiftool; no useful hidden text.
  • Checked for appended payloads with binwalk; no embedded secondary files detected.

At this point, the clue likely involved visual steganography rather than metadata/file concatenation.

Visual Stego Approach​

To reveal hidden content, I generated multiple image transforms:

  • high contrast
  • edge detection
  • channel splits (R/G/B)
  • bit-plane extraction for each RGB channel (bits 0 through 7)

The key step was bit-plane analysis. In the higher bit planes (especially around bit 7), a hidden face becomes clearly visible.

Identification​

The hidden face is Barack Obama.

Final Flag​

DawgCTF{Barack_Obama}

Repro Notes (commands used)​

file hello.webp
exiftool -a -u -g1 hello.webp
binwalk hello.webp
from PIL import Image
import numpy as np

img = np.array(Image.open('hello.webp').convert('RGB'))
for c, name in enumerate(['r', 'g', 'b']):
    ch = img[:, :, c]
    for bit in range(8):
        plane = ((ch >> bit) & 1) * 255
        Image.fromarray(plane.astype('uint8')).save(f'hello_{name}_bit{bit}.png')

Takeaway​

If a challenge says "in plain sight" and metadata looks clean, bit-plane or channel-based visual steganography is often the intended solve path.