SEED CALCULATOR for Reverse engineering (Diag tool development) - Page 1
Forum section: electronics / beginners

author: joelvahans
author_rank: Newbie
timestamp: May 16, 2025, 05:39:38 am
content: Dear Friends,I'm currently working on a project to create a diagnostic tool for Suzuki.I'm doing CAN sniffing between the original Suzuki diag tool and the vehicle via OBD.I have captured "seed keys" generated by the ECU and the "keys" calculated by the diag tool and sent back to this ECU.Can you help me create a seed key calculator from these captured values?ECU : BCMProtocole : UDSPaires Seed → Key :Seed: 0xD147872D → Key: 0x4D8D4344Seed: 0x92C9F7AD → Key: 0x691D7946Seed: 0xD61A5CF8 → Key: 0xDE906FDDSeed: 0x3C71FC5F → Key: 0x58B008ECSeed: 0x2E3DF175 → Key: 0x501D58B8Seed: 0x189ADF61 → Key: 0xE883B21FSeed: 0xCAF6D36D → Key: 0x58C2BD50Seed: 0x25FB5B86 → Key: 0x0A15104CSeed: 0xC4EAAD5F → Key: 0x71365BAASeed: 0xC99FCDF8 → Key: 0x1FAF69A3Seed: 0xE1BF26F8 → Key: 0xFB2E4E92Seed: 0x2B8C8070 → Key: 0xFCE3732A

author: radiolistener
author_rank: Super Contributor
timestamp: May 16, 2025, 06:35:48 am
content: its almost impossible. If you want key generation algorithm, you're need to read documentation or just decompile the code and analyze it

author: darkspr1te
author_rank: Frequent Contributor
timestamp: May 16, 2025, 06:57:35 am
content: if you're willing to pay then you can get what you need from either DigitalKaos forum or MHH Auto forums, they are both pay to access files sites but have what you need.darkspr1te

author: golden_labels
author_rank: Super Contributor
timestamp: May 16, 2025, 07:25:06 am
content: Quote from: radiolistener on May 16, 2025, 06:35:48 amThat’s not true. Not in the general case at least, for this industry.However, if there is any obvious weakness, nowadays it’ll require much more than 12 pairs. You also need somebody willing to spend some considerable effort on finding the pattern. It’s a good place to ask, but be aware you need a ton of luck to find a person having time, drive, and skills to do it for free.The reason for why it’s not “almost impossible,” is that it’s usually not proper security. Not even anywhere close to it. With the exception of IT,(1)until about 2010 in virtually all industries manufacturers blatanly lied about efficacy of their solutions and instead relied on security by obscurity. Due to various factors(2)this started to change in later years. But usually it’s still far from being properly done. In particular in cars there is some hesitance in using cryptographic chips. The threat model the car manufacturers address is also not giving them the incentive to do it any other way: the existing solution is good enough.In this instance, if that N=12 sample is representative, we already can tell this is faked. The first octet in both input and output show some clustering. This should never happen not only with proper cryptography, but with basicPRNGs. It’s worse thanLCG, which points towards ignorant attempts to “improve” some simple generator. As it usually happens, making it much worse.(1)Which doesn’t mean there was no cheating in IT. There was and is, but the situation is much more varied and complicated.(2)For automotive industry the wake-up call was the rise in car theft relying on reproducing sequences generated by key fobs.

author: radiolistener
author_rank: Super Contributor
timestamp: May 16, 2025, 08:33:17 am
content: Quote from: golden_labels on May 16, 2025, 07:25:06 amthen good luck with it, I would be interesting to see some people who can do that with no code decompilation. He is definitely genius...In theory it is of course possible that it uses some simple algorithm with some xor/shifts combination which can be uncovered by spending some time, but I highly doubt it. Usually such things are implemented with some complicated hash and private keys. For example it can be SHA3-512 with output truncation to 32-bit. And the problem is that you even don't know what algorithm it uses.

author: joelvahans
author_rank: Newbie
timestamp: May 16, 2025, 12:48:00 pm
content: Thank you all for your replies

author: golden_labels
author_rank: Super Contributor
timestamp: May 16, 2025, 11:13:21 pm
content: Quote from: radiolistener on May 16, 2025, 08:33:17 amPerhaps, if you read the entire post, you’d know I dedicated 2/3 of the message to explaining why there are low chances it to be SHA3. In fact even MD4 or non-cryptographic hashes like Murmur. With sample N=12 it may be hard to tell, but I would not bet on proper security.Also, SHA3 is a sponge. If one needs 32 bits, one doesn’t use the 512 bit instance in the first place. One uses a 32-bit instance. The digit at the end may be misleading, suggesting SHA3 is thought as a SHA2 replacement. You mentioned it as if it was “stronger, better” SHA. It is not: it’s a different algorithm, going in parallel with SHA2.If only one of them is to survive in the future, SHA3 seems like a better candidate. It has some performance advantages, the ability to output arbitrary length hashes, and may be seen as a better “generic” secure hash due to lower chances of falling into some traps. But it’s also possible that SHA2 will outlive it.