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207 sats \ 4 replies \ @denlillaapan 6 Aug \ on: [ELI5] How does low entropy hurt security? AskSN bitcoin_beginners math science

I thought about this a bunch more, so let me give answering it another shot — by way of analogy, because that's what we do in Bitcoin (shout-out Gigi <3):

  1. the universe: since random, high-entropy private keys are as numerous and rare as any individual atom in the observable universe, we can think about the whole universe and all the stars for an attacker to target. They have no way of uncovering the hundreds of thousands of addresses containing bitcoin, other than searching one planet at a time, looking under one atom (guessing it) to see if it returns a known public key.

If you somehow leak the info that a) Undisc likes Earth, or b) some people appreciate the beauty of a seed phrase poem, you've vaaaaastly reduced the search space for an attacker. (And incidentally, somebody has/is already probing for that) Searching all the atoms on earth takes a while, but nowhere near as long as the universe.
(If you in proper key generation rolled earth, or one of the well-known poems, you're very likely to get fucked)

  1. chess: (obvs... #1467035)

Same thing applies, really, because it's a conversation with the infinite. More possible chess moves/games than observable universe. But if I told you, or an attacker, that my private key is in a sideline off move 18 in the mainline Spanish, all of the sudden there aren't that many candidates left. A bunch of entropy, but only a handful of moves that make sense.
= Chess moves aren't random (they have purpose and intention) so they don't provide entropy, whereas all the possible moves on a board basically is.

how's that?

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135 sats \ 0 replies \ @Scoresby 6 Aug
If you in proper key generation rolled earth, or one of the well-known poems, you're very likely to get fucked

...or to get lucky. It is the same odds as finding a collision with someone else's seed when generating your own.

But this is a fun one to think about!

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74 sats \ 2 replies \ @Undisciplined OP 6 Aug

Let’s dig into the chess analogy a little.

Imagine you base your seed phrase on the configuration of a particular chess board.

An attacker doesn’t have to know that you did that to know someone might and they may decide to search particularly chessy seeming addresses. Fine, that’s not great for security.

What if you start a game with a non-standard board configuration, though? Now your low entropy midgame snapshot won’t look quite so chessy, despite having no more entropy than before. What would make those keys easy to find?

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77 sats \ 1 reply \ @denlillaapan 6 Aug
What if you start a game with a non-standard board configuration, though? Now your low entropy midgame snapshot won’t look quite so chessy, despite having no more entropy than before. What would make those keys easy to find?

probably still quite predictable. Shuffled backrank (Chess960) only has 959 fresh starting positions. Enough to confuse humans out of opening prep but not much for machines. You'll still end up in pretty regular, well-trodden middle games I'd think.

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51 sats \ 0 replies \ @Undisciplined OP 6 Aug

Ok, but maybe the distribution of pieces are different as well as their placement and the game is being played by 6 year olds rather than experienced players.

That’s like adding entropy, but not exactly. The game itself would be similarly limited to common games, while guessing which game is being played converges to impossibility.

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