Cryptoy from GCHQ

The Cryptoy app was designed by Science, Technology, Engineering and Maths (STEM) students on an industrial placement at GCHQ. It was created as part of a project to demonstrate encryption techniques at the Cheltenham Science Festival, and has since been demonstrated at other educational events.

Download from: 

http://www.gchq.gov.uk/how_we_work/partnerships/supporting_education/Pages/Cryptoy-app.aspx