If you want a certain level of privacy from prying eyes on the Text Messages that you send to someone, here’s a Java mobile application that allows you to do just that — send / receive encrypted SMS. The mobile application is actually easy to use enables you to send SMS messages that only the recipient will be able to decipher and read.

CryptoSMS is a J2ME application that allows you to send encrypted SMS to another person. The Java mobile application also solves the problem of having to send out a password to decrypt the message on the receiving end.

CryptoSMS uses a technology called public key cryptography. In a nutshell it’s a kind of encryption/decryption process wherein you use two keys. One key which is the private key stays on your mobile phone and the other key which is the public key is what you distribute to people you want to communicate with.

Using the public key, you can encrypt a message that you can send to that person who holds the equivalent private key. He will be able to decrypt and read it using the private key. Once you and the other party have exchanged public keys, you can start communicating using encrypted messages that will be very hard for other people to decipher.

To start using CryptoSMS, you have to start by generating your private/public key pair. Once you have generated your keys, you can start exchanging public keys with the other person you wish to send / receive encrypted SMS with.

The CryptoSMS J2ME application handles the public key exchange. It is able to check your SMS inbox for public keys that you may have received. If you received the public key of the other person, you can save it and link it to the other person’s mobile phone number.

Sending encrypted SMS messages is easy. Just create the message and select the recipient from the CryptoSMS address book and then send. The mobile application takes care of encrypting and sending the encrypted message.

The separate CryptoSMS address book is also advantageous since it lets you maintain a private address book of mobile phone numbers apart from your normal mobile phone address book.

Reading encrypted messages is also easy since, the mobile application will perform the decryption for you if you are the authorized recipient of the message and you will be able to read the message.

Since the CryptoSMS J2ME application may not be running when the other party sends you an encrypted message, the behavior of receiving encrypted messages depend on your service provider and mobile phone. If the mobile application is not running, your service provider will queue (expiration dependent on the provider) the message until such time that you execute the CryptoSMS application. Some mobile phones will prompt you to run CryptoSMS since there is an incoming message but other mobile phones may not do so.

The CryptoSMS midlet application is still under development but it is already usable. Other features that are planned include key exchange using bluetooth. And I hope a better UI .

If you want to read more about CryptoSMS:

Documentation

Using and installing the cryptosms mobile application

Supported Devices

List of supported mobile phones

CryptoSMS

The cryptosms project web site