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Due to some problems with my Acer Iconia 7 tablet (with KitKat 4.4) I decided to perform factory reset. However, because I have there some data that I did not want to lose I created a backup in HoloBackup. The backup was created succesfully (it has around 1 GB), but when I try to restore it, the process fails by error adb: archive is encrypted but no password given.
Now, at this point, I do not understand, because in developer settings I set a password to protect the backup feature of the tablet. But the error message sounds like a password protection is actually required for the .ab file itself. But in the settings nor in HoloBackup, I cannot see any way how to do it.
Can you help me please. Thank you.

Michael Kůr
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  • when adb backup is executed a dialog prompt appears asking for confirmation. if you leave the password blank the .ab file is unencrypted and extractable with zlib-deflate, otherwise you need java for android-backup-extractor for encrypted backup – alecxs Jul 01 '20 at 22:27
  • While creating a backup, there is no dialog requring a password on the computer screen. The backup process starts immadiately after I unlock the backup function on the tablet. But I want to ask: Is there way to encrypt the file additionally, so it would be accepted by adb.exe? – Michael Kůr Jul 04 '20 at 06:27
  • i didn't say on computer screen, and i mean adb backup. "unlock the backup function on the tablet" is probably the dialog prompt i mean. not sure about HoloBackup – alecxs Jul 04 '20 at 09:31
  • 'adb restore backup.ab' don't requires password for unencrypted backup (leave blank), therefore encrypting afterwards makes less sense. on the other hand encrypted backup is useless without password. go with android-backup-extractor and figure out if your backup is extractable, first – alecxs Jul 04 '20 at 09:36
  • I tried to extract that backup and it works. But to do that, the shell required the password (so the archive was encrypted and protected by the password), which I used to unlock the backup function before. So I do not understand why adb says: "adb: archive is encrypted but no password given" – Michael Kůr Jul 07 '20 at 18:16
  • adb restore backup.ab should ask about password on device screen – alecxs Jul 07 '20 at 19:52
  • When I try it, the restoration process ends immadiately. When I then use .\adb logcat -s BackupManagerService command, i ge this messages: ... W/BackupManagerService( 477): Archive is encrypted but no password given W/BackupManagerService( 477): Invalid restore data; aborting. I/BackupManagerService( 477): Full restore processing complete. D/BackupManagerService( 477): Full restore pass complete. – Michael Kůr Jul 11 '20 at 19:05
  • unpack + repack without encryption – alecxs Jul 11 '20 at 20:11
  • or, maybe there is a way to give password via command line when calling /system/bin/bu directly (can't tell you have no access to computer) https://android.stackexchange.com/q/142533 – alecxs Jul 13 '20 at 09:27
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    Thank you, now it works; unpack and repack without encryption was enough. Thanks again. – Michael Kůr Jul 14 '20 at 15:50
  • consider posting detailed steps as answer to your own question – alecxs Jul 14 '20 at 17:07

1 Answers1

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Thanks to alexcs I was able to get it working, so here are the steps to solve the issue:

  1. You need to convert the .ab file to unencrypted .tar archive, first. To do that, follow next steps.
  2. If you have not installed Java SE on your computer yet, download it and install.
  3. Download android-backup-extractor from SourceForge and extract it.
  4. Now open Windows Explorer and locate the folder, to which you unpacked that archive.
  5. Navigate to ...\android-backup-tookit\android-backup-extractor\android-backup-extractor-20180521-bin
  6. Open the folder, where is located your .ab backup, in a new window and copy the abe.jar executable from android-backup-extractor-20180521-bin folder and paste it here.
  7. Now open command-line or Windows PowerShell and use the cd "path" command (for example cd "C:\omegavesko-HoloBackup-179d978\Backups" to change your parent directory to the folder, in which is stored your .ab file
  8. Now convert the .ab file to unencrypted .tar archive by entering this command: java -jar abe.jar unpack [file name of the original .ab file] [file name of the output file],(for example java -jar abe.jar unpack backup_june_2020.ab output.tar).
  9. Now unlock the .ab file by entering password, which should be the same as the password you are using to unlock the backup function of your device.
  10. Wait, until the process is not finished (the size of the .tar file will stop grow) .
  11. Now convert the .tar file to unencrypted .ab file, using command: java -jar abe.jar pack [file name of the converted backup file] [file name of the new .ab backup](for example: java -jar abe.jar pack output.tar backup_june_2020_fixed.ab)
  12. Wait, until the process is not finished.
  13. Now navigate to the directory, where is executable HoloBackup.exe (for example cd "C:\omegavesko-HoloBackup-179d978")
  14. Now power on your android device, connect it via USB and eventually make other neccesary settings.
  15. Restore the backup by using command .\adb restore "file path" (for example adb restore "C:\omegavesko-HoloBackup-179d978\backups\backup_june_2020_fixed.ab")
  16. Enter the password on your device to unlock the backup function.
  17. Wait until the process finishes.
Michael Kůr
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