Hiding in Plain Sight 2 — MetaCTF

Description

Something here seems a little off, can you figure out what? The flag will be the name of the person or object you find, such as DawgCTF{Turkey_Sandwich}

English summary: we are given a PNG image (ps2.png) and told that something hidden inside it should identify a person or object. The goal is to recover that hidden subject and format the answer as a DawgCTF{...} flag.

Source: https://metaproblems.com/9158c536955b3b93c3b1ec47841cc0ff/ps2.png

Analysis

The first pass was standard image reconnaissance.

• The file was a valid PNG.
• Dimensions were 2400x1350 with RGBA channels.
• There was no useful EXIF metadata.
• PNG chunk inspection showed a normal structure.
• There was no appended payload after the PNG end.

That ruled out the easy cases: hidden archives, obvious metadata leaks, or malformed-file tricks.

Because the first "Hiding in Plain Sight" style challenge used a hybrid-image effect, I also tested the usual visual transforms:

• Gaussian blur
• aggressive downscaling / resizing
• grayscale conversion
• pixelation / block averaging

Those checks were reasonable, but they were not the decisive path here. They did not cleanly reveal a second face or object the way a classic hybrid image would.

The breakthrough came from bit-plane analysis. Extracting the low-order bit planes of the RGB channels revealed that the least-significant-bit view contained an embedded image. The strongest result was the combined RGB bit-0 output (ps2_rgb_bit0.png), where the left side clearly showed a hidden human figure.

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