TextSecure can replace a standard application for SMS, encrypting the messages. Moreover, no it is not necessary to do root.
Now we are witnessing a real boom in communications systems for mobile phones - WhatsApp, LINE, Facebook Messenger, Viber and others have uncovered a real Pandora's box. Next we will see a boom in the form of communications systems that will ensure the security of the transmission and the inability read your messages or representatives of the security services, nor "Gopnik" and anyone at all except the sender and recipient. Today's Android application allows you to replace the standard application for SMS, encrypting the messages. Moreover, no it is not necessary to do root.
That you sent an encrypted message was read by the recipient, it is necessary that he, too, was found TextSecure application. By the way, TextSecure is open source and everyone paranoid can check its reliability for its super-critical correspondence.
Messages before sending encrypted locally before being sent and stored as encrypted. So if your phone is stolen, no one can read your correspondence.