Samsung SCH-I515MSAVZW - Manual (Page 104)

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When you're ready to turn on encryption:
1 From a Home or All Apps screen, touch the Settings icon .
2 Touch Personal > Security > Encryption > Encrypt phone.
3 Read the information about encryption carefully.
The Encrypt phone button is dimmed if your battery's not charged or your phone's not plugged in.
If you change your mind about encrypting your phone, touch the Back button.
Warning! If you interrupt the encryption process, you will lose data.
4 Touch Encrypt phone.
5 Enter your lock screen PIN or password and touch Continue.
6 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'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.