Here’s who probably did that $150 million Bitcoin transaction • Hacker News Board

Re: Here’s who probably did that $150 million Bitcoin transaction

#111

Post by tlrobinson » Mon, Nov 25, 2013, 12:18 AM UTC

sillysaurus2 wrote: post #93

waps wrote: post #83

Earlier quoted context omitted.

I don't think so. Brainwallets are generated as a hash. So if the input is secure, the output is secure. It's not possible to generate the input from the output. And frankly the connection between password -> private key and private key -> public key is very similar in brainwallets. To crack a brainwallet, given only the public key and sufficient bits in the password, is actually harder than directly attacking the pr…

To crack a brainwallet, given only the public key and sufficient bits in the password, is actually harder than directly attacking the private key. It's incredible to see such misinformation on HN. I suggest you read this: https://dl.dropboxusercontent.com/u/315/articles/A%20Large-S... This is a 2007 study on web password habits. In it, they reveal the fact that fewer than 1% of passwords have bitstrength >= 90 bits:…

Brainwallets shouldn't be casually recommended without appropriate warnings, but they certainly can be secure.

Passphrases aren't limited by length, and your brainwallet can be derived from your memory and publicly available information, so you can construct very strong memorable passphrases, e.x. the 3rd sentence of the 8th chapter of your favorite book concatenated with a moderately strong but memorable password.

Key stretching with PBKDF or scrypt helps a lot as well. Do you care if it takes 1 minute to compute your keys from the passphrase? Probably not, and it will make cracking much more difficult.

Re: Here’s who probably did that $150 million Bitcoin transaction

#112

Post by chm » Mon, Nov 25, 2013, 4:33 AM UTC

anigbrowl wrote: post #110

chm wrote: post #61

Earlier quoted context omitted.

Any investment is speculation until proven otherwise. And by that I mean that "the mass" accepts it as an "investment".

I'm distinguishing it from investments that pay a dividend or interest coupon at time of purchase, or which have a commodity value independent of price (eg gold and oil are commodities that you can speculate in or take delivery of for actual consumption). You might well get rich from speculating in bitcoin, but if if doesn't pan out then your assets could end up having no value whatsoever - you won't even be able to…

Then we agree that it is a very risky investment and one should be careful about it =)

Re: Here’s who probably did that $150 million Bitcoin transaction

#113

Post by meowface » Mon, Nov 25, 2013, 10:08 AM UTC

waps wrote: post #83

meowface wrote: post #78

Earlier quoted context omitted.

It's completely infeasible (without quantum computers anyway). However, in cases where the private key is generated from a hash of a passphrase, like brainwallets, then it is far more feasible. There are people running bruteforcers constantly looking for private keys corresponding to brainwallet passphrases; that's their form of "mining". To test it, if you make a brainwallet with a password of "password" and then se…

I don't think so. Brainwallets are generated as a hash. So if the input is secure, the output is secure. It's not possible to generate the input from the output. And frankly the connection between password -> private key and private key -> public key is very similar in brainwallets. To crack a brainwallet, given only the public key and sufficient bits in the password, is actually harder than directly attacking the pr…

You missed my point. You can't attack the cryptographic function or the keyspace, but you can attack the original passphrase that is hashed, via typical hash cracking methods (rainbow tables, bruteforcing, dictionary attacks, etc.). All you need to know is the hash function; most brainwallets use a single round of SHA256.

Re: Here’s who probably did that $150 million Bitcoin transaction

#114

Post by meowface » Mon, Nov 25, 2013, 10:09 AM UTC

asperous wrote: post #89

meowface wrote: post #78

Earlier quoted context omitted.

It's completely infeasible (without quantum computers anyway). However, in cases where the private key is generated from a hash of a passphrase, like brainwallets, then it is far more feasible. There are people running bruteforcers constantly looking for private keys corresponding to brainwallet passphrases; that's their form of "mining". To test it, if you make a brainwallet with a password of "password" and then se…

You are right and here's why: Brainwallet inputs -> public keys are deterministic. It's true that the method of creating the key pair is as much of a password as the password, it's easy to select the most common methods (sha-256 hashes, bitaddress.org's method, etc.) I cracked thousands of passwords for the https://keybase.io/warp competition (I lost by a few minutes... the answer to the top one is Je). Once you have…

I've also noticed quite a few people who've posted threads on bitcointalk after having fallen victim to one of these brainwallet crackers. It really boggles the mind why someone would entrust significant amounts of money to an incredibly weak passphrase.

Re: Here’s who probably did that $150 million Bitcoin transaction

#115

Post by meowface » Mon, Nov 25, 2013, 10:10 AM UTC

tlrobinson wrote: post #111

sillysaurus2 wrote: post #93

Earlier quoted context omitted.

To crack a brainwallet, given only the public key and sufficient bits in the password, is actually harder than directly attacking the private key. It's incredible to see such misinformation on HN. I suggest you read this: https://dl.dropboxusercontent.com/u/315/articles/A%20Large-S... This is a 2007 study on web password habits. In it, they reveal the fact that fewer than 1% of passwords have bitstrength >= 90 bits:…

Brainwallets shouldn't be casually recommended without appropriate warnings, but they certainly can be secure. Passphrases aren't limited by length, and your brainwallet can be derived from your memory and publicly available information, so you can construct very strong memorable passphrases, e.x. the 3rd sentence of the 8th chapter of your favorite book concatenated with a moderately strong but memorable password. K…

Even extending to a 1-second computation would make it completely infeasible to crack. 1 minute would be way overkill.

Re: Here’s who probably did that $150 million Bitcoin transaction

#116

Post by kaoD » Mon, Nov 25, 2013, 3:53 PM UTC

shock-value wrote: post #20

DanBC wrote: post #19

Earlier quoted context omitted.

> anonymous and private transactions Something doesn't have to be private to be anonymous. So if you're happy with anonymous and public it's possible, but hard.

In theory yes, but as the linked blog-post shows, Bitcoin---in its current state anyway---likely isn't truly anonymous either (ostensibly due to its transactional records being public).

Then it's just not-private, but still anonymous (I don't need to disclose my name to get a Bitcoin address).

Re: Here’s who probably did that $150 million Bitcoin transaction

#117

Post by tlrobinson » Mon, Nov 25, 2013, 5:06 PM UTC

meowface wrote: post #115

tlrobinson wrote: post #111

Earlier quoted context omitted.

Brainwallets shouldn't be casually recommended without appropriate warnings, but they certainly can be secure. Passphrases aren't limited by length, and your brainwallet can be derived from your memory and publicly available information, so you can construct very strong memorable passphrases, e.x. the 3rd sentence of the 8th chapter of your favorite book concatenated with a moderately strong but memorable password. K…

Even extending to a 1-second computation would make it completely infeasible to crack. 1 minute would be way overkill.

Well, whether it's overkill depends on how weak your passphrase is.

Re: Here’s who probably did that $150 million Bitcoin transaction

#118

Post by exo762 » Fri, Dec 06, 2013, 12:53 PM UTC

superuser2 wrote: post #109

exo762 wrote: post #99

Earlier quoted context omitted.

> Spending on sex toys is not special, unless the national security apparatus (or more likely your competitor in the private sector) already has a reason to try to discredit you. Which is a valid concern for activists, but not most people. Amazing. Translation: "Rights are essential for small group of people, because everyone else is not exercising them anyway. So lets just take the rights away".

From where do you derive a right to hide your finances from a government whose power to levy an income tax is explicitly codified in the Constitution?

1) Bitcoin is incredibly more transparent than banking system or tax system. If anything, it is not convenient for tax evaders. HSBC, however, managed to launder 200bln of drug money.

2) I'm a person. I have to pay taxes. Top500 corps - not so much, in practice. What do you say about that?

3) Where the fuck did you get that I'm a tax evader? I was addressing your point about people's rights and your evaluation of their need of having those rights.