HILL is an adaptive spatial-domain steganography method for uncompressed images. It assigns embedding costs from the image content, so modifications are directed towards areas where they are expected to be harder to detect.
Use in tools
HILL was used by HStego versions prior to 0.4 for uncompressed images. This should be read as a method implemented by that tool version, not as a separate algorithm named “HStego 0.3”.
For detectability experiments, StegoWatch also relies on the HILL simulator included in Aletheia. A separate HILL research implementation is available in StegoLab.
Detectability results
In the evaluated setting, the HILL simulator is much less detectable than simple LSB replacement methods. Its relative position against S-UNIWARD depends on the payload range shown in the chart.
Simulator-based results should be interpreted as method-level results. Embedding simulators are usually slightly harder to detect than real end-user tools such as HStego, because they embed close to the theoretical limit and do not include all practical constraints of a complete tool.