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[Q] How to edit a stock ROM and pass verification

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jeremyb234
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Cool [Q] How to edit a stock ROM and pass verification

Feel free to answer as much or as little of this post as possible. My desire is to learn. First, let me phrase my question in general terms:

1. Is it possible to download a stock android firmware rom, extract the rom, and change it, and repackage it in a way that is still accepted by the device as an original factory ROM? In other words, is it possible to take a factory rom (such as an update.zip or in my case 1.0.7.zip) and change it and reinstall it in the stock android system recovery (3e)?

Now that I have asked the general question, I will explain to you why I want to do this (if possible)

I have a tablet that recently stopped booting. I have never rooted it or used a custom rom before. However, the device still powers on and I can access the stock android recovery system. I can even use ADB (though I know very little about it's capabilities). I will explain my logic below. Please feel free to show me if I am wrong on the following points.

1. It is impossible to install a custom rom without FIRST installing a custom recovery.
2. It is impossible to install a custom recovery without FIRST rooting the device.
3. It is impossible to root a device that won't boot if you do not have USB Debugging enabled (via Android Developer Options).

The manufacturer of my device (RCA RCT6378W2) has not released the source code or original factory firmware for this device. I have attempted to install various roms that seem to be compatible via ADB SIDELOAD, but they have always been rejected immediately after the device says:
Finding update package...
Opening update package...
Verifying update package...
Installation aborted.
However, I have managed to located 3 firmware updates from RCA. These updates are called 1.0.2.zip , 1.0.3.zip, and 1.0.7.zip. These updates are all accepted by the android system recovery. When I ADB Sideload these updates, the tablet says this:
Finding update package...
Opening update package...
Verifying update package...
Removing unneeded files...
Unpacking new files...

Install from ADB complete.
Although these firmware updates are installed properly, my tablet still does not boot. Upon closer examination of these updates, they are not full android OS firmwares, but mere updates to the existing system. So, this got me to thinking... These updates are the only firmwares that can manage to pass update verification. Is it possible to alter these updates in a way that will still pass this verification process? If this is possible, then I might be able to reflash the rest of the android operating system by altering these updates to include the full OS. Does anyone know if this is possible? What would be the difficulty level of doing so? I have managed to locate nearly all of the files from another user who has the same device in working condition. For example, I have the following from a working device:
Backup.img
boot.img
cache.img
kernel.img
kpanic.img
misc.img
parameter.img
parameter.txt
recovery.img
system.img
Would it be possible to take the files from these images and add them to the firmware updates and repackage it in a way that passes system verification? And my last question is: Is there any other way I can get this device to a working version of android (stock, custom, I don't care!). Thanks!
 
dreamwave
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There is unfortunately no way currently to modify a manufacturer signed zip and still have it signed unless you have friends within the company who can get you that signature. If you want to root your phone first you need to unlock the bootloader then use fastboot while in bootloader/odin/download mode and flash a recovery then you can use a custom rom.
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jeremyb234
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Quote:
Originally Posted by dreamwave View Post
There is unfortunately no way currently to modify a manufacturer signed zip and still have it signed unless you have friends within the company who can get you that signature. If you want to root your phone first you need to unlock the bootloader then use fastboot while in bootloader/odin/download mode and flash a recovery then you can use a custom rom.
Thanks for the info. If there is no way to alter a manufacturer rom in a way that is accepted by the system, then I might be out of luck. I don't know much about bootloaders. I feel like I heard someone say that this device did not have one. I've also heard that this device doesn't support fastboot and that Nexus is one of the few that does (that might have been an old statement... not sure). Anyways, it might be time for me to give up on this device. Thanks for the clarification.
 
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Quote:
Originally Posted by jeremyb234 View Post
Thanks for the info. If there is no way to alter a manufacturer rom in a way that is accepted by the system, then I might be out of luck. I don't know much about bootloaders. I feel like I heard someone say that this device did not have one. I've also heard that this device doesn't support fastboot and that Nexus is one of the few that does (that might have been an old statement... not sure). Anyways, it might be time for me to give up on this device. Thanks for the clarification.
what device is it? I'll see if I can find a guide
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jeremyb234
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Quote:
Originally Posted by dreamwave View Post
what device is it? I'll see if I can find a guide
Thanks for the help. It is a RCA RCT6378W2. It is 7" and 8GB. Lots of info on the following link:

http://specdevice.com/showspec.php?i...3-c58700000000

How about this question- On a non-rooted device with standard android recovery system, is there any way to install another rom... perhaps one from a very similar device?
 
dreamwave
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Quote:
Originally Posted by jeremyb234 View Post
Thanks for the help. It is a RCA RCT6378W2. It is 7" and 8GB. Lots of info on the following link:

http://specdevice.com/showspec.php?i...3-c58700000000

How about this question- On a non-rooted device with standard android recovery system, is there any way to install another rom... perhaps one from a very similar device?
no, as it has to be signed by the manufacturer to be accepted by the recovery, and I don't see any roms or even recoveries for your device...
Flamers and Trolls may break my bones but thanks will always help me...

 
jeremyb234
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Originally Posted by dreamwave View Post
no, as it has to be signed by the manufacturer to be accepted by the recovery, and I don't see any roms or even recoveries for your device...
Thanks for checking up on that for me. I've learned alot in my process of trying to fix my tablet, but I think it's about time to call it quits

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