You can use the Pocket Engima Machine app to encrypt pretty much anything – texts, emails, notes to your opposite number in Moscow – using a system of changeable rotors.
It’s a simulation of a 3-rotor Enigma machine used in the Second World War and, like the real thing, Pocket Enigma Machine only works if both you and the person you’re sending your messages to know these settings.
Again like the Enigma machine, there are five different ‘rotors’ to choose from and you can change their starting positions. For further levels of encryption you can change the position of each of the alphabetical ‘rings’ in relation to the rotors and pair up letters in the plugboard (AQ, DX, SP, etc).
Confusing right? Well, it took the men and women of Bletchley Park more than a few minutes to figure it out too. This Wikipedia article (which is helpfully reproduced within the app) and this YouTube video provide more detailed explanations of how the machine (and therefore the app) works.
Pocket Enigma costs $2 (£1.25) from the Android Market.
One more thing: TQVGXVO GFA SDX NAG ZSS ESF
(Rotors: I, II and III, Start position: R, E, C, Rings: O, M, B Plugboard: not used)