Image and audio steganography: channels and extraction hypotheses

Mechanism

Steganography hides data within another representation rather than necessarily encrypting it. Potential channels include pixel bit planes, palettes, metadata, appended bytes, sample least-significant bits, and frequency-domain patterns. A promising visual pattern should lead to a specific extraction hypothesis with a defined channel, ordering, and encoding.

Practical method

Check the container and metadata first, then compare expected and actual file length. Inspect separate color channels and bit planes without resaving the source. For audio, examine a spectrogram and sample properties. Try one extraction ordering at a time and validate output structure before applying further decoding.

channel -> bit position -> pixel/sample order -> byte grouping -> decoder
record all five choices for a reproducible extraction

Interpreting evidence

A recognizable file header or coherent message supports the hypothesis more strongly than isolated printable bytes. Compare alternate bit orders and check that the claimed payload length fits the available capacity.

Pitfalls and limits

Lossy re-encoding destroys many spatial channels. Screenshots change pixels and metadata. Running many blind decoders produces chance patterns that should not be reported as confirmed hidden content.