$npx -y skills add zhaoxuya520/reverse-skill --skill competition-stego-mediaInternal downstream skill for ctf-sandbox-orchestrator. CTF-sandbox workflow for image, audio, video, document, and container steganography. Use when the user asks to inspect metadata, alpha or palette channels, LSBs, thumbnails, appended trailers, QR fragments, transcoding artif
| 1 | # Competition Stego Media |
| 2 | |
| 3 | Use this skill only as a downstream specialization after `$ctf-sandbox-orchestrator` is already active and has established sandbox assumptions, node ownership, and evidence priorities. If that has not happened yet, return to `$ctf-sandbox-orchestrator` first. |
| 4 | |
| 5 | Use this skill when the challenge lives inside a media container, hidden channel, or appended payload rather than a conventional crypto blob. |
| 6 | |
| 7 | Reply in Simplified Chinese unless the user explicitly requests English. |
| 8 | |
| 9 | ## Quick Start |
| 10 | |
| 11 | 1. Confirm the real container type, dimensions, duration, codec, and chunk layout before guessing a hidden layer. |
| 12 | 2. Check metadata, thumbnails, sidecar files, and appended trailers before deeper signal-domain work. |
| 13 | 3. Rank candidate channels by evidence: alpha, palette, LSB, transform-domain residue, frame order, or container slack. |
| 14 | 4. Preserve each extracted layer separately so the transform chain stays reproducible. |
| 15 | 5. Stop when the hidden payload is reproduced, not merely suspected. |
| 16 | |
| 17 | ## Workflow |
| 18 | |
| 19 | ### 1. Establish Container Truth |
| 20 | |
| 21 | - Inspect headers, chunk tables, EXIF or document metadata, container indexes, thumbnails, and file size anomalies. |
| 22 | - Compare declared format against observed structure to catch polyglots, appended archives, or malformed trailers. |
| 23 | - Record exact offsets, frame numbers, or channel boundaries that look promising. |
| 24 | |
| 25 | ### 2. Inspect Candidate Channels |
| 26 | |
| 27 | - Check alpha, palette order, RGB or YUV planes, LSBs, spectrogram features, document object streams, or video frame deltas. |
| 28 | - Prefer evidence-driven attempts over brute forcing every transform. |
| 29 | - Note whether the payload is plain bytes, another media layer, compressed data, or an encrypted blob. |
| 30 | |
| 31 | ### 3. Reconstruct The Hidden Payload Path |
| 32 | |
| 33 | - Keep the chain in order: container -> channel or carrier -> extraction -> decompression or decode -> final parse. |
| 34 | - Separate extraction success from final interpretation; a channel hit is not the same as artifact recovery. |
| 35 | - If the problem becomes primarily about cryptography after extraction, hand off to the broader crypto skill. |
| 36 | |
| 37 | ## Read This Reference |
| 38 | |
| 39 | - Load `references/stego-media.md` for the media checklist, channel ranking guide, and evidence packaging. |
| 40 | |
| 41 | ## What To Preserve |
| 42 | |
| 43 | - File structure facts: offsets, chunks, frame numbers, stream names, metadata keys, and trailer size |
| 44 | - Intermediate extractions and the exact command or transform used to produce them |
| 45 | - The final recovered payload and the channel that produced it |