[dm-crypt] No key available for this passphrase

Sebastian r4p.t0x at googlemail.com
Fri Jan 25 18:53:19 CET 2013


Hello,

I have quite a problem here with my notebook (debian squeeze and luks/dm-crypt
encrypted LVM).
After shutting it down yesterday, it did not let me unlock the encrypted disk
this morning.

I already found the post from September 2012 in the mailing list, but it did not
exactly match my case (everything looks fine, not overwritten by SWAP data)


Header Information looks OK to me:

 # cryptsetup luksDump /dev/sda2
LUKS header information for /dev/sda2

Version:        1
Cipher name:    aes
Cipher mode:    cbc-essiv:sha256
Hash spec:      sha1
Payload offset: 2056
MK bits:        256
MK digest:      53 44 c2 4d b0 9e c5 73 ef fa d7 12 4f dd f0 75 64 3b 88 ad 
MK salt:        50 5f a9 69 21 6e 21 ac db 09 bd 79 b0 9b 9b 1e 
                14 2a 5d e4 46 2b 4d 9c 49 e3 9f 7d f9 d7 64 84 
MK iterations:  10
UUID:           b89fe8ad-3aea-4f27-9448-06e75fd8a05a

Key Slot 0: ENABLED
        Iterations:             75899
        Salt:                   2d 2b 66 4c 57 eb ff e7 7f 63 14 8f c5 3b 6b aa 
                                38 53 2d 52 52 b6 d9 cc 84 b0 1a 11 bd cf 88 70 
        Key material offset:    8
        AF stripes:             4000
Key Slot 1: DISABLED
Key Slot 2: DISABLED
Key Slot 3: DISABLED
Key Slot 4: DISABLED
Key Slot 5: DISABLED
Key Slot 6: DISABLED
Key Slot 7: DISABLED


Looking closer to the header (exported to file via luksHeaderBackup), right
after the initial information also shown by luksDump up to address 0x1000 (first
keyslot) is filled with zeroes, from 0x1000 until the end of the file random
data with no ASCII that would indicate files (e.g. header informations) or a
partition table.

The key slot checker though, gives me this output:


./chk_luks_keyslots /home/r4pt0r/notebook/luksheader.img

Sectors with entropy below threshold (0.850000):

Keyslot 0: start:   0x1000 
  position:  0x10000   entropy: 0.625023

Keyslot 1: start:  0x21000 
  keyslot not in use

Keyslot 2: start:  0x41000 
  keyslot not in use

Keyslot 3: start:  0x61000 
  keyslot not in use

Keyslot 4: start:  0x81000 
  keyslot not in use

Keyslot 5: start:  0xa1000 
  keyslot not in use

Keyslot 6: start:  0xc1000 
  keyslot not in use

Keyslot 7: start:  0xe1000 
  keyslot not in use



So the entropy seems to be too low? But where does the address 0x10000 come
from? shouldn't the key start at 0x1000 similar to its slot?


I HAD an backup of the header on USB stick - the Notebook was set up around 3-4
years ago but i really found my old backup-stick (32MB) where also gpg-keys and
other small files were backed up. 
BUT: the stick seems to be broken :(  It's not recognized by any PC and the LED
doesn't light up...



As the Notebook is usually put to sleep-mode I really can't remember what
updates were installed since the last reboot.



Is there any possibility the key is not damaged and data can be recovered?

Thanks for any help!

Sebastian



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