[Verizon Samsung Galaxy S III] TrevE:
Hey guys - good seeing some of the old HTC guys over here (and all the new faces). As you all probably know i've been lurking around helping behind the scenes working on the rom. I have been researching the IMEI loss issue lately with the help of some Synergy testers (thanks guys) and have came up with the following information.

Now I do not have a gs3 myself, nor do I know anyone that has lost their imei (with said blocks to restore from), so its all "untested". Consider this a warning and continue on doing whatever other redundant methods to be safe.

<start geek details>

There are several important keys on the system, HDCP keys, WIFI/Bluetooth MAC, Playready DRM keys, and IMEI/radio NV data. Our backups goal is to get all of these full partitions and have an easy restore process.

Paths/Files that appear to be important:

[B]Playready DRM:[/B]
/efs/drm/playready/bdevcert.dat
/efs/drm/playready/devcert.dat
/efs/drm/playready/license.hds

[B]Wifi Mac used by macloader:[/B]
/efs/wifi/.nvmac.info

[B]HDCP (untested, anyone have HDMI cable?)[/B]
/efs/cert.cp
/efs/hdcp13.bin

[B]radio/nvdata partitns:[/B]
13-modemst2 & 20-backup
12-modemst1 & 21-fsg

[B]Unknown (may be important dumps):[/B]
/data/misc/radio/

Now the important question here, nvdata/imei. The EFS partition has been verified by itself not to be a valid backup/restore of imei. This is because not all the files "actually" live there.

/efs on disk partition 11 reports to contain

/.files
/FactoryApp
/bluetooth
/drm
/imei
/sensors
/wifi

The actual EFS contains

/CGPS_ME
/CGPS_PE
/CGPS_SM
/CGPS_TLE
/SUPL
/application_specific_profiles
/cert
/client-cert
/client-key
/eHRPD
/gnss
/hdr
/mmgsdi
/mmode
/nv
/nvm
/pdp_profiles
/sd
/shared
/sms
/ssm
/wlan

So whats with the difference? After changing some radio values and checking partition MD5s we narrowed it down to a few moving partitions. More light was shed on this by going back to bootloader R&D, we can see Adam got an interesting email from someone named lee who analyzed the param.img structure. (if hes still around, would love to hear more on this) What is interesting now to us that wasn't during bootloader R&D are these few reboot reasons:

What these show is modemst1 backs up to fsg part, modemst2 goes to backup. These must be important partitions if they are duplicated/backed up. The other key part here is sets param_header.nvdata_backup to 1, nvdata being the important bits that contain imei among other things.

</end geek details>

Now as I said before, I see this as being more of a "total backup" for keys. I have not been able to thoroughly test this because its hard to reproduce the loss, but I have good faith from what we have seen that restoring modemst1/modemst2/efs/data folders to a known good state together hopefully would restore service. Please continue using other methods as well as a "double safeguard"

The next unlucky soul to loose their imei I would love to see run through the restore steps. On flash of rom - starting with tonights nightly - we will be creating a unsigned updater-zip formatted file with a backup of important partitions in /sdcard/synergyrom/. if you are left with a bad imei or any other bad keys, move the latest .zip where you know you had a good imei from /sdcard/synergyrom/backups/*.zip to the root of your SD card and flash it (and of course let us know here if it worked!)

Good luck!

*EDIT* I have attached a signed copy of the updater.zip we were using for testing to this post. It contains all the tools to backup your important partitions to synergyrom/backup folder on your SDCard. It creates an unsigned 7ziped files in flashable format.you can use to try to recovery from bad imei/mac/drm keys. Use common sense/with care, I wouldnt restore unless you are sure things have gone downhill (or balls of steel)