How to decrypt adopted storage.

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. You can read it with this command: hexdump -e '1/1 "%.2x"' the_key_file.key

   
   



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 <Put the 16-byte hex key here> 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.