How to Lock Text Messages on an iPhone Without Jailbreakingby Terry Parker
You can lock text messages, as well as other personal data, on your iPhone without jailbreaking your phone and voiding your Apple warranty. The iPhone is shipped with the “Passcode” feature. When you enable this feature, you will need to enter the passcode to reset your phone, to wake the phone or to turn the phone back on after restarting. Be sure to remember your passcode because you will need to reset the phone to factory defaults if you forget it.
Open the iPhone’s Springboard screen and then tap the “Settings” icon. The Settings screen opens.
Tap the “General” option and then tap the “Passcode Lock” option.
Tap “Turn Passcode On.” The Passcode feature is enabled.
Type a four-digit passcode into the input box and then retype the code to confirm. The Passcode feature is now enabled on the phone. You will need to enter this passcode in order to turn on, restart or wake up your phone. Your text messages and all personal information are now protected.