external sd - How to decrypt Adopted Storage?

Using the SD card as Adopted Storage encrypts it. How can it be decrypted?

Answer

1. Your device must be rooted.


2. Using a file browser like ES Explorer, browse to /data/misc/vold.



3. The .key file there is the encryption key of your adopted storage.


4. Open that file with a hex editor to view the 16-byte key.


5. On any GNU/Linux distro you can do this first mount your SD card, in my case SD card was mounted at /dev/sdb2.


6. 
   

   Then run this command:

   
   

   dmsetup create crypt1 --table "0 `blockdev --getsize /dev/sdb2` crypt aes-cbc-essiv:sha256  0 /dev/sdb2 0"
   

   
   

   Some types of errors/warnings can be ignored.

   
   


7. 
   
   

   If your key is correct you can mount it by mount -t ext4 /dev/mapper/crypt1 /mnt/1/

   
   


8. Finally you can run cd /mnt/1 to browse the decrypted storage.