Enigma Simulator: Fully functional, accurate simulator of the infamous German Enigma encryption machine invented in 1918.
GnuPG: Port of GnuPG (Privacy Guard) by Steffan Bellon.
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.
PhotoSteg: Will disguise any type of data within pre-drawn RISC OS 24- or 32-bit sprites.