PGP and Security Utilities - A collection of security utilities for RISC OS. Includes front ends for PGP, allowing PGP to be used for e-mail and files. - http://www.queen.clara.net/pgp/acorn.html
PhotoSteg - Will disguise any type of data within pre-drawn RISC OS 24- or 32-bit sprites. - http://web.ukonline.co.uk/david.thomson/riscos/software.html
Enigma Simulator - Fully functional, accurate simulator of the infamous German Enigma encryption machine invented in 1918. - http://www.xat.nl/enigma/
GnuPG - Port of GnuPG (Privacy Guard) by Steffan Bellon. - http://www.sbellon.de/gnupg.html