A Dynamic Visualisation of the DES Algorithm and a Multi-faceted Evaluation of Its Educational Value

There is a general consensus that visualisations can be effective in teaching, compared to traditional modes of instruction. Encryption offers an interesting case study for the application of visualisation, largely due to its complex and abstract nature. This paper is concerned with the presentation of a dynamic and interactive visualisation of the Data Encryption Standard (DES) algorithm, and the evaluation of its educational value. Its design was motivated by the desire to seamlessly bridge the gap between algorithm formulation and its visualisation, and to provide instruction in context. As DES is an archetypal cryptographic algorithm, a visualisation of its operations on confusion and diffusion is a key requirement. The educational value of the visualisation is expressed in terms of four facets: its educational effectiveness, its presentation as an interactive and dynamic graphical object, its perceived usefulness by students and its completeness as a learning resource. Educational effectiveness was assessed in terms of the pre-test and post-test scores of a treatment group and a control group of students, whereas the other three facets were evaluated through a survey taken by the treatment group. An analysis of the results of the evaluation of the visualisation confirms its educational value.