Secure SMS description

I remember when one of my friends asked me to see my android phone, when he was checking he saw my inbox and one of the SMS had password of one secret access sent by my colleague.

Since the content in SMS was plain text the message was visible, though it didn't harm me too much but at that time I thought to have a mechanism by which the SMS goes encrypted and remains encrypted in default inbox in the phone.

The app Secure SMS lets you send a secure SMS to the recipient with a passphrase and the encrypted message can be seen through the app if decrypted successfully using that passphrase.

The passphrase here needs to be agreed by both the parties or can be communicated through some other media.