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entropy

Challenge​

Imported from local notes.md.

Solution​

Original Notes​

entropy

Challenge Summary​

  • Given: A live ANSI maze service at nc 34.131.216.230 1340.
  • Goal: Reach the red target cell before the 5-second collapse.
  • Constraints: The board redraws continuously, the player resets after the collapse timer, and input pacing is not faithful FIFO when flooded.

Initial Recon / Triage​

  • Observations:
    • Start position is (1,1) and the target is (49,49).
    • d moves right and s moves down from the start. Invalid keys cause redraws without movement.
    • Same-connection 5-second windows differed by hundreds of mask cells, which did not support the idea of a tiny reusable template set.
  • File identification:
    • artifacts/probe_entropy_path.py: trace live paths from a candidate route.
    • artifacts/scan_entropy_motifs.py: scan repeated d/s steering motifs.
    • artifacts/compare_entropy_round_templates.py: compare stationary masks across collapse windows.
    • artifacts/attempt_entropy_route.py: retry a promising route until the service prints a flag.
  • Entry points:
    • Live service only.

Hypotheses & Approach​

  • Hypothesis 1: The maze might come from a small template family that could be fingerprinted and solved offline.
  • Hypothesis 2: If template reuse was not strong enough, a repeated steering pattern could still land close enough to the target to win occasionally.

Outcome:

  • Template clustering stayed noisy even with multi-frame denoising and same-connection comparisons.
  • The best live route family was a repeated ddss motif followed by a long d tail.

Execution Steps (Reproducible)​

Stage 1​

Commands:

cd /root/incognito2026CTF/entropy
python3 artifacts/collect_entropy_templates_multiframe.py --samples 16 --read-window 1.4 --min-frames 6 --cluster-threshold 24
python3 artifacts/compare_entropy_round_templates.py --rounds 3 --max-seconds 18

Results:

  • Fresh-session and same-connection mask distances were both large, so no small template family was proven.

Stage 2​

Commands:

cd /root/incognito2026CTF/entropy
python3 artifacts/search_entropy_patterns.py
python3 artifacts/sample_entropy_pattern.py "$(python3 - <<'PY'
print('ddss'*80 + 'd'*240)
PY
)" --trials 20 --duration 5.5 --stop-score 97

Results:

  • The route ddss repeated with a long d tail produced a near-solve leg ending at (49,48).

Stage 3​

Commands:

cd /root/incognito2026CTF/entropy
python3 artifacts/attempt_entropy_route.py "$(python3 - <<'PY'
print('ddss'*80 + 'd'*240)
PY
)" --trials 20 --duration 5.6

Results:

  • Trial 7 returned the flag while reporting a final parsed player position of (49,48).
  • The service output contained:
IIITL{K4l31d05c0p3_M4z3_M4573r_9921_n0_3y35_41c0b0c61792}

Artifacts Produced​

  • artifacts/compare_entropy_round_templates.py
  • artifacts/attempt_entropy_route.py
  • artifacts/probe_entropy_path.py
  • artifacts/scan_entropy_motifs.py
  • artifacts/sample_entropy_pattern.py

Flag​

IIITL{K4l31d05c0p3_M4z3_M4573r_9921_n0_3y35_41c0b0c61792}