Emojibius — broncoctf2026

Description

Our intelligence agency has intercepted a strange transmission. It looks like Gen-Z developed a new language. We found a cryptic image of an elderly person on a nearby server?? Can you recover the secret message?

Hint: Sometimes you can tell what's written all over someone's face.

Two artifacts are provided:

• intercepted_signals.txt — a single line of space-separated emoji pairs.
• artifact.png — a 2816x1536 close-up of an elderly person's face. Five header emojis (🍎 🦊 🍐 🐶 🎈) run across the forehead, and a faint 5x5 character grid is written across the face.

Goal: recover the hidden message.

Analysis

The title Emojibius is the key clue: Emoji + Polybius. This is a Polybius square cipher where the row/column coordinates are encoded as emojis instead of digits.

• The ciphertext uses exactly 5 distinct emojis, and each token is a pair — classic Polybius (row, col) coordinates.
• The image supplies the missing pieces the "written all over someone's face" hint points to:

  • The 5 header emojis on the forehead define the axis order (index 0-4 for both rows and columns): [🍎=0, 🦊=1, 🍐=2, 🐶=3, 🎈=4]

  • The 5x5 character grid written on the face is the Polybius square content:

    b r o n c
    { e m 0 j
    1 s _ g 3
    } a d f h
    i k l p q
    

Each intercepted pair (row_emoji, col_emoji) maps to grid[row][col].

Solution

Map every emoji to its header index, then look up the grid cell for each pair.

#!/usr/bin/env python3

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