CryptoSMS - protect your SMS (Android only)

For a long time, somehow, already in the distant 2011, deciding on Android programming, I decided to write an SMS encryption program. And after reading the article New MegaFon service - reading remote SMS remembered this program and thoughts on its development ...

So, first, a little about the program itself: pretty primitive, and so far the usual XOR is used as cryptography.
The main functions are to encrypt and send a text message and decrypt the received one.
For encryption, you must select the contact to whom you want to send the message (so far only one contact), type the message itself and enter the password on which this message will be encrypted, and then click "Send":

Do not forget to provide the password to the recipient, otherwise it will be difficult to read your message :-).
When a message arrives, in the standard interface it will look something like this:

You can read the message again from the application being described: select the message that we are going to read, enter the password, and click the Read button:

After that, the message will look like:

At the same time, the message is only shown in decrypted form, in the phone storage it remains encrypted.
This description of the program can be completed.

As the development of the application I wanted to implement a full-fledged cryptography, and asymmetric (with public and private keys), add functionality for exchanging public keys. But so far the hands have not come to understand cryptography :-).

PS Regarding the publication on Google Play, there are doubts, since there is still a hint of cryptography - if anyone came across, consult, pliz.
')
PPS If someone is interested and wants to try, then you can download it here . Comments and constructive criticism are welcome.