Google Galaxy Nexus Android mobile technology platform 4.0 Users Guide - Manual (Page 103)

101
Encrypt your phone
You can encrypt all the data on your phone: Google Accounts, application data, music and other media,
downloaded information, and so on. If you do, you must enter a numeric PIN or password each time you
turn on your phone. Note that this is the same PIN or password that you use to unlock your phone
without encryption, and cannot be set independently.
Warning! Encryption is irreversible. The only way to revert to an unencrypted phone is to perform a factory data reset,
which erases all your data.
Encryption provides additional protection in case your phone is stolen, and may be required or
recommended in some organizations. Consult your system administrator before turning it on. In many
cases the PIN or password you set for encryption is controlled by the system administrator.
Before turning on encryption, prepare as follows:
1 Set a lock screen PIN or password.
2 Charge the battery.
3 Plug in your phone.
4 Schedule an hour or more for the encryption process: you must not interrupt it or you will lose some
or all of your data.