Gm Seed key algorithms

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Re: Gm Seed key algorithms

Postby gmtech825 » Tue Dec 15, 2020 5:45 am

so with rolling seed/key, does the seed roll as well or just the key? On the E 41 I have, After programming it, the seed did not change, I haven't been able to test to see if the key changed after.

also, don't some ECU's lock out after multiple failed key attempts, causing the auto generate method to take even longer?

Thanks for the discussion, I find this stuff all very interesting. I have no real plans to try and do anything with the info.

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Re: Gm Seed key algorithms

Postby Tazzi » Tue Dec 15, 2020 9:40 am

gmtech825 wrote:so with rolling seed/key, does the seed roll as well or just the key? On the E 41 I have, After programming it, the seed did not change, I haven't been able to test to see if the key changed after.

also, don't some ECU's lock out after multiple failed key attempts, causing the auto generate method to take even longer?

Thanks for the discussion, I find this stuff all very interesting. I have no real plans to try and do anything with the info.


Both seed/key are rolling. Meaning the calculation is taking place inside the ECUs firmware. So attacking the ECU firmware SHOULD be the go to, but because the microcontrollers are locked down, you cant get into the juicy stuff to even reverse them.

ECUs like E41 use the single 5byte seed/key.
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Re: Gm Seed key algorithms

Postby mattyjf01 » Sat Jan 02, 2021 3:14 pm

Ve Series 2
EHU:
GM_Other
ALGO: 0B

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Re: Gm Seed key algorithms

Postby ironduke » Sun Jan 03, 2021 1:49 am

Seed: 1234
Algorithm: 0b

GM other selected

Step : tempseed1 = seed << 0x2
Step : tempseed2 = seed >> 0xE
Step : seed = (tempseed1 | tempseed2)
Step : seed += 0xB6B6
Step : Byte Swap Seed
Step : seed-= 0xFDDA

Seed: 0x1234 Key: 0x8925 Algorithm: 0xB


This look good to anyone else??? Do we have known good seed/key combos to test with??

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Re: Gm Seed key algorithms

Postby mattyjf01 » Sun Jan 03, 2021 2:40 pm

I meant
If you want to put a Series 2 IQ EHU In
Unlock with Algo 0b from GM_Other
Then write lower 8 VIN with ID 28 :D

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Re: Gm Seed key algorithms

Postby mattyjf01 » Sun Jan 03, 2021 4:01 pm

GMLAN

E77
ALGO: 0B

VE BCM
ALGO: 7C

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Re: Gm Seed key algorithms

Postby The1 » Thu Jan 07, 2021 1:45 pm

ironduke wrote:Seed: 1234
Algorithm: 0b

GM other selected

Step : tempseed1 = seed << 0x2
Step : tempseed2 = seed >> 0xE
Step : seed = (tempseed1 | tempseed2)
Step : seed += 0xB6B6
Step : Byte Swap Seed
Step : seed-= 0xFDDA

Seed: 0x1234 Key: 0x8925 Algorithm: 0xB


This look good to anyone else??? Do we have known good seed/key combos to test with??


This is from a Barina XC or Corsa C with E55 type ecu if it helps. Class 2 algo B

60 36 seed
41 78 key

94 60
95 E0

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