[FAQ] Custom ROM and S-OFF (Security-OFF) on HTC Android Devices

Written by Fridza. Posted in Developer

Published on November 10, 2011

Are you planning to flash your HTC phone with a custom ROM ? That’s mean you need to gain S-OFF (Security-OFF) on your phone. Some of you might be curious what is S-OFF, so we decide to write a FAQ about it. Thanks for gtrab from xda-devs, who provide the faq for Desire Z.

1. What is Bootloader and how to enter it ?
The Bootloader is a firmware management tool, on HTC device a bootloader has several function, it let you to reset your phone to factory default, flash official ROM, launch recovery utility.
If you want to go to bootloader you have to disable Fast boot first (go to Settings > Power > Fastboot) or remove the battery. Turn off your phone and then hold power button + volume down button together till white screen appears.

bootloader htc droid s-off

2. Custom Recovery, What is it ?
Every shipped HTC phones already come with stock recovery which accessible through bootloader, but the stock lack of features so we need much better recovery. ClockWorkMod is an example of most used custom recovery, the main features are full backup and flashing unsigned/custom/unoffcial ROMs, but requires root privileges and S-OFF.

3. What it is and Why I need S-OFF to flash a ROM ?
You should know that every shipped HTC devices has additional security check called Security-ON (S-ON), it will verify signature image for almost any ROMs right before it written into android system area. By change it to Security-OFF (S-OFF) you can bypass this security check and let you install/flash any ROM or custom android recovery application. This is not the same as “root” but both is needed in flashing process.

4. Will change my security to S-OFF void my warranty ?
You can actually revert it to S-ON if you want, maybe your warranty still valid after you change it to default, but it depends your manufacturer policies.

5. If I change my mind, can I revert to S-ON ?
Yes you can, but the methods depends on HTC device model. Some HTC smartphone or tablet model are able to change it to S-ON again by flashing the stock (official) RUU. It’s recommended to performing short research before planning to do this.

6. Exactly what is a custom ROM ?
ROM is stands for Read Only Memory also known as firmware, and located into internal storage and contains Ramdisk, Kernel, Radio Image Android OS and all stock apps. Custom ROM means a ROMs which modified by users, so it’s unofficial.

7. What exactly is RUU ?
RUU stands for ROM Update Utility. It’s an official flashing tool for HTC devices, and generally consist of full firmware and executable flashing tool to run from computer.

[Source : xda-devs]
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