Encrypted SMS (Caeser Cipher)

[adrian peirson]

Found out about App inventor last week, was intrigued and started playing, thought I'd try a simple SMS encryption app based on the simplest
form of encryption, the Caesar Cipher (which is highly unsecure) 
I've attached the aia file CipherSMS1E.aia

Now it's 'completed' I might see if I can introduce some more secure Ciphers into it.

It detects incoming encrypted files by checking for a three char string that's attached to all scrambled messages, the three chars are '/*%'
If it doesn't detect that string at the beginning of an incoming message, it doesn't display it.
The basic operation is...enter your message to be encrypted, enter the recipients tel no, press Scramble,
it will then scramble the message using the simple caesar cipher.
Press Send SMS and all being well, your encrypted message should be sent.
I've included a few error traps but it doesn't handle all characters, and falls over if it encounters a character it hasn't been coded for.
The characters it will accept are ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 ,./\[]{}()!"£$%&*@:;<>_-=+?'#

I might try to add other ciphers like railfence etc.

PS I'm not a cryptographer.

It seems to work reasonably well

Regards Adrian.


PS I'm using App Inventor 2

[adrian peirson]

PS, if I wanted to give this app away for others to download, what sites would I be allowed by licensing to upload to, Google Play, F-Droid etc ?
I don't have a Dev account at google as this is my first app.

[Enis]

Creating a dev account on Google Play, especially if you're not charging for anything, is pretty easy to do.  You can also post AIA files up here, but not APK files...

[adrian peirson]

Thanks, I will look into it.
I understand there is a $25 fee to set up a developer account, is that correct ?

Regards.

[Enis]

Yes, that's correct... it's a one time fee...