J-UNIWARD is an adaptive JPEG-domain steganography method. It assigns costs to changes in JPEG DCT coefficients using a distortion function designed for the JPEG domain.
Use in tools
J-UNIWARD was used by HStego versions prior to 0.4 for JPEG 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 J-UNIWARD simulator included in Aletheia. A separate J-UNIWARD research implementation is available in StegoLab.
Detectability results
In the evaluated setting, the J-UNIWARD simulator is substantially less detectable than older JPEG tools such as Outguess and F5, and also less detectable than Steghide under the same conditions.
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.