Zte Grand S Flex User Manual page 28

4. Enter your lock screen PIN or password and touch Next.
5. 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 completed, you're 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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