Steganography
Sweep an image, audio file, or paragraph for hidden data across the whole technique space rather than guessing one method.
By the end you can
- Extract LSB data across channels, bit orders, and traversal directions
- Read a spectrogram to distinguish painted text, Morse, SSTV, and DTMF
- Detect zero-width and whitespace steganography in plain text
- Explain why LSB survives in PNG and dies in JPEG
1. Read
2. Use the tools
In the order they come up while solving. Each opens the workspace tab that runs it.
Automatic steganography solver
Throw every applicable steganography technique at a file at once - image, audio, archive, text, and document - recursively unpack what falls out, and surface flag matches.
LSB steganography extractor
Extract least-significant-bit data from images across every channel, bit order, and traversal direction, with bit-plane visualisation.
Audio spectrogram and SSTV decoder
View a WAV as a spectrogram to find text drawn in frequency space, decode Morse and SSTV, and extract LSB data from audio samples.
Zero-width character and text steganography decoder
Reveal messages hidden in zero-width Unicode characters, trailing whitespace, and homoglyph substitution - text steganography that survives copy-paste.
3. Try one now
Generated in your browser and checked in your browser. No account, nothing to download, and a fresh one whenever you want another.
Practice
generated here, checked here, no account and nothing to download
4. Practise on the real thing
Real picoCTF challenges that use these techniques, easiest first. 29 match in total - see the full index.
Checkpoint
Solve a nested stego challenge and draw the chain of containers from the outermost file to the flag.
Teaching note
Steganography rewards breadth, which makes it the module where an automated sweep is most obviously better than a hypothesis. Use it to teach that a broad cheap search beats a narrow expensive guess.