CyphrTxt for Blackberry is a great little app for those seeking to keep the information flowing between contacts private.

Add an extra layer of security to your BlackBerry.
Encrypt your emails and PIN plain text with AES 256-bit encryption. Messages will be sent, received and saved as encrypted and can only be decrypted by the owner of the encryption key. The key is protected by an encrypted password. Once the plain text message is encrypted it will not appear in plain text on your BlackBerry again. The receiver of the encrypted messages must have CyphrTxt installed and select the same encryption key option as the sender.
CyphrTxt is fast and easy to use.

Features:
AES 256-bit encryption approved by NSA for top secret information.
Can be used for email-messages and PIN messages.
Saves only encrypted text.
Can be set to prompt for encryption key at each sending and receiving occasion.

Minimum Requirements:
Minimum Operating System 4.5 or greater
Disable Compatibility Mode for Storm and Storm 2

Display Dimensions
320×240, 360×480, 480×320, 480×360
Operating System
4.5, 4.6, 4.7 Non-Touch, 4.7 Touch Screen, 5.0 Non-Touch, 5.0 Touch Screen

$4.99
CyphrTxt