4 ms·

I did an easier version of this in my college intro class. There was a class competition that involved rock paper scissors as a subcomponent, and ties were brok

by strstr 10d ago

I did an easier version of this in my college intro class. There was a class competition that involved rock paper scissors as a subcomponent, and ties were broken with randomness. You could rig Java’s prng so you would win all ties. The prng was seeded with usec time at first call. I called the rng a bunch of times to harvest entropy, and scanned the plausible usec times to find the seed. Then I primed the prng so I would win ties. Frankly, I assume I implemented this wrong, but the theory was there lol.

rogueaine 10d ago
That’s not at all what the article proposed. The author constructed and transpose to the linear shift register coefficients and built a circuit network based on this to predict the next state (in the sandbox) and direct recipes.
- strstr 10d ago
  From the article: > Sampling the current RNG through observations, > Computing the current internal RNG state, > Predicting the future internal states, > Calculating corresponding quality levels for each future call, and finally > Making use of the predicted levels with some adapters. The entropy->seeds (internal RNG state) step took more math of course. Frankly, I wouldn’t be surprised if they could have extracted the seeds without the math with a bit of RE and memory inspection. The version I did wasn’t predicting quality of course, it was predicting tie breakers
3eb7988a1663 10d ago
I am failing to find the article, but some early online poker systems used the server time as the seed coupled with a weak PRNG. With the information of the hole cards + community cards, after a few hands, could quickly determine exactly what seed was being used and perfectly predict everyone's cards.
- e28eta 10d ago
  I don't think this was the original source, but this paper matches your (& my) recollection: https://gwern.net/doc/cs/cryptography/2006-arkin.pdf https://gwern.net/doc/cs/cryptography/2006-arkin.pdf google surfaces a couple of HN posts, but the source (cigital.com) seems to be a dead domain at this point: https://news.ycombinator.com/item?id=288138 https://news.ycombinator.com/item?id=288138 https://news.ycombinator.com/item?id=9914607 https://news.ycombinator.com/item?id=9914607 It's a bad shuffle implementation + using time of day as seed (reducing search space). Using the player's 2 cards and the 3 flop cards, it finds the RNG seed in real time, and then future hands (on the same server) are solved in "under one second!"
  - 3eb7988a1663 9d ago
    Indeed this is not the article I originally read either, but very similar breakdown of the problem.

by strstr 10d ago

rogueaine 10d ago

That’s not at all what the article proposed. The author constructed and transpose to the linear shift register coefficients and built a circuit network based on this to predict the next state (in the sandbox) and direct recipes.

strstr 10d ago
From the article: > Sampling the current RNG through observations, > Computing the current internal RNG state, > Predicting the future internal states, > Calculating corresponding quality levels for each future call, and finally > Making use of the predicted levels with some adapters. The entropy->seeds (internal RNG state) step took more math of course. Frankly, I wouldn’t be surprised if they could have extracted the seeds without the math with a bit of RE and memory inspection. The version I did wasn’t predicting quality of course, it was predicting tie breakers

3eb7988a1663 10d ago

I am failing to find the article, but some early online poker systems used the server time as the seed coupled with a weak PRNG. With the information of the hole cards + community cards, after a few hands, could quickly determine exactly what seed was being used and perfectly predict everyone's cards.

e28eta 10d ago
I don't think this was the original source, but this paper matches your (& my) recollection: https://gwern.net/doc/cs/cryptography/2006-arkin.pdf https://gwern.net/doc/cs/cryptography/2006-arkin.pdf google surfaces a couple of HN posts, but the source (cigital.com) seems to be a dead domain at this point: https://news.ycombinator.com/item?id=288138 https://news.ycombinator.com/item?id=288138 https://news.ycombinator.com/item?id=9914607 https://news.ycombinator.com/item?id=9914607 It's a bad shuffle implementation + using time of day as seed (reducing search space). Using the player's 2 cards and the 3 flop cards, it finds the RNG seed in real time, and then future hands (on the same server) are solved in "under one second!"
- 3eb7988a1663 9d ago
  Indeed this is not the article I originally read either, but very similar breakdown of the problem.