Telstra EASYTOUCH 4G User Manual page 20

The Encrypt phone button is not available if the battery is not
sufficiently charged or your phone is not plugged in.
If you are unsure about proceeding then touch the Back Key.
WARNING! If you interrupt the encryption process, you will lose
data.
6. Touch Encrypt phone.
7. Enter your lock screen PIN or password and touch Next.
8. Touch Encrypt phone again.
The encryption process starts and displays its progress.
Encryption can take an hour or more, during which time your
phone may restart several times.
When encryption is complete, you are prompted to enter your
PIN or password.
Subsequently, you must enter your PIN or password each time
you power on your phone, to decrypt it.
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