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Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
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Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
#22I have seen a lot of interesting and funny RNG issues, but this is one of the most sophisticated exploits for the least payout. A wonderful work of art.
If they had sold the items they could have probably made some money (maybe $1000s?). Still a small payout considering the amount of work, of course.
Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
#23Back in 1999-2000 there was an "International RoShamBo Programming Competition" [1] where computer bots competed in the game of rock-paper-scissors. The baseline bot participant just selected its play randomly, which is a theoretically unbeatable strategy. One joke entry to the competition was carefully designed to beat the random baseline ... by reversing the state of the random number generator and then predicting…
That's me! Thanks for pulling up the quote from long ago:
> "With his obvious technical skill, and his "cheat early and often" attitude, Tim could have a promising career as an AI programmer in the computer games industry. :)"
Instead took a path of security, authoring the TLS RFC and principal engineer in Google security. Thanks for the flashback.
Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
#24Back in 1999-2000 there was an "International RoShamBo Programming Competition" [1] where computer bots competed in the game of rock-paper-scissors. The baseline bot participant just selected its play randomly, which is a theoretically unbeatable strategy. One joke entry to the competition was carefully designed to beat the random baseline ... by reversing the state of the random number generator and then predicting…
That's me! Thanks for pulling up the quote from long ago: > "With his obvious technical skill, and his "cheat early and often" attitude, Tim could have a promising career as an AI programmer in the computer games industry. :)" Instead took a path of security, authoring the TLS RFC and principal engineer in Google security. Thanks for the flashback.
Only on Hacker News!
Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
#25Earlier quoted context omitted.
I think I never used PRNG in any serious software, but it surprised me as intuitively I would've assumed that using the same RNG in as many places as possible would make it harder to perform such an attack, because it would make it less likely you can observe enough places at which it is updated, but this was a pretty impressive and fun demonstration that this is false.
Pretty much all serious software uses PRNG at some point. Unless you mean you use CSPRNG, which is the easy fix.
Yeah it's obviously biased to the field you work in. And I'm aware that libs im using use some form of randomness, be it for uuid-gen, entropy for SSL or whatnot, but I seriously can't remember the last time I called rand() and friends directly for anything.
Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
#26Back in 1999-2000 there was an "International RoShamBo Programming Competition" [1] where computer bots competed in the game of rock-paper-scissors. The baseline bot participant just selected its play randomly, which is a theoretically unbeatable strategy. One joke entry to the competition was carefully designed to beat the random baseline ... by reversing the state of the random number generator and then predicting…
I submitted the optimally bad entrant the first year, cheesebot.
https://web.archive.org/web/20180719050236/http://webdocs.cs...
Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
#27Pretty cool exploit. The idea of a free for all bug abusing server is pretty neat, a whole ‘nother level of the game. I guess this is what “actually fighting” (rather than just using in-game battling mechanics) would look like if the metaverse really happened ever.
> The idea of a free for all bug abusing server is pretty neat, a whole ‘nother level of the game.
Balance converging around bugs and exploits is pretty typical for all PvP sandbox games with cutthroat gameplay, even if not allowed by the server. ARK: Survival Evolved and Eve Online are infamous for having huge clans (thousands of players) willing to go extreme lengths at metagaming and bug exploitation. It isn't always that rosy, ARK had certain mechanisms to dox players and their multiple Steam accounts, which I believe led to a few spillovers of the ingame relations to the real life during the Great War. Sometimes it's very basic stuff though, like building a huge tower and breaking it upon being raided, DoSing the server and crashing it, after which it rolls back to a previous backup made 10-20 min ago, making your base very hard to raid if you have active players. (an ancient thing that was fixed many years ago)
Rust (the PvP game, not the language) also had the policy of encouraging players to spread and publish bugs and exploits on YouTube, but with the different aim - so that the devs would notice and patch those faster. This resulted in a pretty robust game that is extremely hard to exploit without resorting to actual external hacks.
Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
#28Back in 1999-2000 there was an "International RoShamBo Programming Competition" [1] where computer bots competed in the game of rock-paper-scissors. The baseline bot participant just selected its play randomly, which is a theoretically unbeatable strategy. One joke entry to the competition was carefully designed to beat the random baseline ... by reversing the state of the random number generator and then predicting…
The whole commentary about the "supermodified" class of competition entrants is making my laugh: > Nostradamus was written by Tim Dierks, a VP of Engineering at Certicom, who has a lot of expertise in cryptography. The program defeats the optimal player by reverse-engineering the internal state of the random() generator, which he states "was both easier and harder than I thought it would be". To be sporting, it then…
I was very curious about the Psychic Friends Network. One can find the code here (https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...), and it's easy to deobfuscate substantially by running it through the C preprocessor.
I believe it works as follows: - It plays randomly for the first 998 turns (https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...): this line is "if (*turn - In the last 2 turns, it uses `find_goodkarma` to comb through the stack to find where the variables that match its history and the opponents' history are stored. These the stack arrays p1hist and p2hist (https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...)
They're easy to find because they contain 998 known values each in a ~random sequence of (0, 1, 2), and they're just upwards of the stack from the current invocation of the Psychic Friends Network.
`find_goodkarma` simply increments a pointer until the whole sequence of 998 values matches the known history.
- Then, it rewrites the history to make itself win. These lines (https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...) never get executed, then these lines (https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...) tally up draws so far (libra), wins (cancer) and losses (scorpio).
This line makes sure its move is the opponents' move +1 mod 3, which is the winning move: https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...
Then, these lines repeat the same trick for the number of wins and losses. It checks whether it's p1 or p2 by comparing the addresses of the win/loss arrays, and then overwrites the wins/losses appropriately using `pizza` https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...
in the end it returns an arbitrary value (the address of `good_hand` mod 3).
It was fun to follow but the result is kind of boring :)
Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
#29The video looks very much like a particle collider’s detector output.
Re: Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG
#30The video on this is amazing: https://www.youtube.com/watch?v=maMpMOnIJDE. I had no idea how sophisticated the community was.