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More Fun DS2431 DRM Stuff!!!

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I asked some questions last week about reverse engineering a consumables management chip on a DVD buffing machine. That project has been since abandoned because the boss man went with new machines from a different company... with very similar DRM measures. This time around they use a 1 wire EEPROM, a DS2431 to be exact. The manual says that removing a chip before the 800 minute buffing time is used up renders the chip useless. I have found that powering the machine off before removing the chip circumvents this. I will include dumps of 3 different chips. I used a raspberry pi 4 to dump the contents using a write up i found. When looking at the dumps, the contents of the chip did not change with each buffing cycle. This makes me wonder if the data on the EEPROM is just a key and not something that keeps count of cycles remaining. I am thinking of using a logic analyzer to sniff the traffic between the chip and machine. I do not have a logic analyzer currently, and don't know which model I should go with. I saw a reddit post on a similar topic and the folks in that subreddit said that the people in the eevblog forums eat this type of thing up. THanks for all the help!

Likely those are just unique keys and the actual time remaining is stored in the machine itself, not written to the EEPROM in the consumable. So probably there is an EEPROM in the machine itself which keeps track of which keys have been used up.

Do you have more than one machine of the same model? Try inserting a "spent" chip from one machine into the other and see if it work. If so, then that would prove the theory that the data is actually stored in the machine not in the consumable chip.

ooh good idea. im going to try that now

I'd open the machine and search for a EEPROM, you might make a dump before and after changing the consumable, It could be as easy as making a reset circuitry that writes the EEPROM with a push button.

For the logic analyzer:

For a 1-wire bus, the cheapest LA will do.


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