vulcan-cryptanalysis

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The first step in our process was to acquire several DVP modules and a DVP key loader, both of which are inexpensive and readily available on eBay and at ham fests. We then examined the DVP modules to identify the purpose of the various ICs these modules contain. Our attention quickly focused on an IC labeled only with a Motorola logo and bearing the identifier SC76807 (see Figure 2). Figure 2: SC76807 Integrated Circuit Unlike plastic IC packages, which require strong acids to unveil the die, the SC76807 uses a ceramic and metal chip carrier package that can be de-capped with a large soldering iron. Once we removed the metal lid, the die was exposed for our inspection (see Figure 3). We imaged the die at a magnification of 200 using a metallurgical microscope and a digital camera, resulting in a clear view of the top metal layer of the die. We quickly determined that the SC76807 is a medium scale integration (MSI) metal gate CMOS chip of large geometry, typical of mid to late 1970s IC process technology. Although we did not count the individual gates, this is a fairly simple device, well within the ability of a single individual to analyze. Once we had an image of the M1 layer of the SC76807, we began analyzing the various circuits and their functions. Due to the large amount of repeated circuitry, this task was not nearly as time-consuming as we had originally expected. Our detailed analysis of the SC76807 IC follows in Section 2. Once we fully understood the workings of the SC76807, we realized that this knowledge by itself was insufficient for a complete understanding of DVP. This is because the DVP key loader plays a significant role in the overall operation of DVP. We therefore had to obtain a DVP key loader and perform some reverseengineering on it as well. Like the SC76807, the DVP key loader was easy to reverse-engineer, although in this case it was primarily software rather than hardware that we had to reverse-engineer. After reading the firmware ROM and disassembling the code, we quickly discovered the portions of this software that determine how the 71- 6
7 Figure 3: SC76807 Die Shot
Page 1 and 2: Vulcan: A Proprietary Cipher of the
Page 3 and 4: As a final comment concerning Motor
Page 5: known how vulnerable this cipher ac
Page 9 and 10: of the SC76807 in a later section,
Page 11 and 12: At the far right side of the chip i
Page 13 and 14: signal. The WE input on Pin 9 and t
Page 15 and 16: its and are always set to 0 by the
Page 17 and 18: 4 DVP Key Loader Based on our analy
Page 19 and 20: 4.2 Reverse Engineering Understandi
Page 21 and 22: 5.1 Key Schedule We created an Octa
Page 23 and 24: plaintext bit (i.e. we are mounting
Page 25 and 26: cryptovariable in real time solely
Page 27 and 28: exposed, it would be enlightening i
Page 29 and 30: [6] Motorola Encryption Topics, htt
Page 31 and 32: % form 8-bit data word from 7 bits
Page 33 and 34: B Vulcan Encrypt Simulation %------
Page 35 and 36: D Vulcan Cryptanalysis Simulation %
Page 37 and 38: 0,1,0,0,1,0,0,0,0,1,0,0,0,1,0,1,0,1
Page 39 and 40: 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
Page 41 and 42: c = bitxor(c,bitand(cv8(7),ctd(nn-2
Page 43 and 44: E DVP Key Loader Firmware Disassemb
Page 45 and 46: F09A : BD F1 C0 " " jsr $F1C0 put t
Page 47 and 48: F166 : 5C "\" incb F167 : 20 F9 " "
Page 49 and 50: F22C : CE FF 9D " " ldx #$FF9D Load
Page 51 and 52: -----------------------------------
Page 53 and 54: F3B9 : 81 04 " " cmpa #$04 F3BB : 2
Page 55 and 56: F48B : 39 "9" rts -----------------
Page 57 and 58:
F553 : 39 "9" rts -----------------
Page 59 and 60:
F62C : 8E F8 E2 " " lds #$F8E2 tab:
Page 61 and 62:
F707 : 7E F9 10 "~ " jmp $F910 disp
Page 63 and 64:
F7CA : 97 82 " " staa PB F7CC : 96
Page 65 and 66:
F87F : 08 " " inx F880 : D6 74 " t"
Page 67 and 68:
F947 : 97 82 " " staa PB F949 : 88
Page 69 and 70:
FA05 : 5A "Z" decb FA06 : 26 F4 "&
Page 71 and 72:
FAE4 : 27 03 "’ " beq $FAE9 FAE6
Page 73 and 74:
FBC8 : 27 05 "’ " beq $FBCF . . .
Page 75 and 76:
FC80 : 01 " " nop FC81 : D6 74 " t"
Page 77 and 78:
FD31 : 20 08 " " bra $FD3B --------
Page 79 and 80:
. . . . . . . . . . . . . . . . FE0
Page 81 and 82:
FEAD : 27 04 "’ " beq $FEB3 FEAF
Page 83 and 84:
FF61 : BD F1 70 " p" jsr $F170 writ
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