Comment by trotsky | Hacker News Reader

Comment by trotsky | Hacker News Reader

Users mostly can't be trusted to produce reasonably constructed 8 character passwords even when there are complexity requirements. So it's rather surprising to hear that now it's a good idea to fully derive the key protecting your spends like cash edollars based off of a pass phrase that's simple enough they feel comfortable committing it to memory. Hint: you'll find a signifiacnt number of pass phrases if you brute force with only phrases out of popular books people will have lying around. You don't even need to wait for them to make their key first - since this is effectively unsalted go ahead and generate your bitcoin brainwallet rainbow tables ahead of time. Then just set your bot to watch for keys in use that you've previously generated. Hell, consider that this is effectively like having a website that only asks for pass phrase for login and no username - given how many people pick password1 as their passwords you're almost sure to see people colliding accidentally with the first 16 words in their favorite psalm or chapter 6 of the twilight book.

It's really easy to keep your keys secure and off disk and still be able to use great entropy - they're called smart cards.

You're right, but I think you miss the point of this article.

The point is that one could store in his brain all the information needed to pay and receive any amount of money, without needing any extra storage device.

Because this money is Bitcoins, and because they are not stored anywhere, it technically means that all your money, all your wealth, resides in your brain - hence the title "Brainwallet".

This is a fascinating thought experiment, but not an assessment of the most secure way to store money.

Can't wait for the opportunity to lose my entire savings in a two-minutes backstreet incident.

Better use this only for the equivalent of todays's purse with as much cash as you feel you need for the next few days.

See also http://news.ycombinator.com/item?id=2551397 for how to mitigate such risks.

I still remember a disused http://world.std.com/~reinhold/diceware.html passphrase I generated some ten years ago. Even though it's gibberish, using whole words seems to help a lot.

http://xkcd.com/936/

pass phrases do provide a better source of memorable entropy as compared to traditional passwords, but look at the result the the comic comes up with. In this context, where the pass phrase isn't associated with a user name and the "hashes" are globally published pass phrases made up of four common english words would be relatively trivially brute forceable.

Also note that most people following similarly given instructions would actually construct a pass phrase in the form of "subject adverb verb predicate" or "subject verb adjective predicate" or a few other constructions, dramatically reducing the implied entropy of the phrase.

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