White hat hacker releases Bitcoin brainwallet skimmer that can guess 130,000 passwords per second

What is a brain wallet? A brain wallet is an iterative type of Bitcoin wallet in which the password is not stored digitally, but in the user's memory.

Brainwallets, originally conceived to keep sensitive wallet data offline and make Bitcoin addresses easier to remember, use a single long password and phrase that converts it into a private key, a public key, and an address.

Are brain wallets safe? It seems not safe. A white hat hacker has released a tool whose purpose is to illustrate the insecurity of brain wallets. This tool uses an offline attack method to quickly guess possible passwords to see if they are correct.

Ryan Castellucci, a security researcher at digital anti-fraud company White Ops, published the study, pointing out that brain wallets have major flaws. He stressed that the final Bitcoin address is recorded on the blockchain as a password hash. When the password hash is used for website authentication, it helps you determine whether the word or phrase provided is correct, which means that this data can be used by hackers as a reference to find passwords.

Castellucci unveiled the brain wallet decryption tool, called Brainflayer , at DEF CON 23, one of the world’s largest annual hacker conferences, on August 7, and it can guess 130,000 passwords per second. According to Castellucci, the software can check 5.6亿个短语密码for 1美元on a powerful computer.

Castellucci said that when the brute force cracking software is applied to ASCII passwords and XKCD passwords, which are four-character passwords, a botnet can check all Bitcoin addresses that have received funds in a day.

In the interview, Castellucci stressed that while his tool could be used by criminals, he hopes its release will encourage bitcoin users to adopt better, more secure practices.

Following the release of the tool, BrainWallet.org, a website that used JavaScript to generate user private keys, decided to go offline, a move that was widely praised by members of the Bitcoin security community.

Origin of the project

According to Castellucci, the idea for the project first came about in mid-2013, when bitcoin users first raised security concerns about using brainwallets.

Around the same time, a white hat hacker on Reddit going by the name btcrobinhood began stealing funds from brainwallet users and then returning those stolen funds to the owners in an attempt to expose vulnerabilities in the technology.

Inspired by this, Castellucci created a primitive version of Brainflayer that was able to guess 10,000 passwords per second, a far cry from the current Brainflayer capabilities. Still, he recalls, the simple program still achieved outstanding results.

When he returned to his computer, he discovered that the prototype version of Brainflayer had retrieved 250 BTC , or $20,000 worth of Bitcoin.

Castellucci said he faced a moral dilemma and he didn't know what to do.

“For a while I stopped my research,” he said. “I hoped the problem would go away on its own. After all, many experts were saying that brain wallets were bad.”

But the problem did not go away, so he decided to return to his research.

He wrote in a recent blog post:

"My idea is that if someone finds a bug like I did, they'll work hard to get it fixed before sharing it with the world. I've done that in the past, and I think it's the right way to go."

suggestion

In addition, he suggested that those who are using brain wallets should consider WarpWallets , which is currently considered an improved iteration of the product. The generator of warpwallet can use Keybase, for example, so that users no longer have to save or store their private keys anywhere, they just need to pick "a good password".

With WarpWallets, the " salt ," or random data used in the hashing function, is built into the equation, Castellucci said. That means if a user's salt is their email address, a potential thief would need to have both the salt and their password to steal the funds.

Of course, Castellucci also recommends that those who use such wallets use diceware to generate passwords, which produces passwords through a pair of dice and a random number generator.

"It seems like it's going to be very hard to get people to stop using things like their dog's name and their birthday as passwords, and Scrypt won't save people who use 'P@ssw0rd' as their password," he said. "A lot of people seem to think that a long password is a secure password, and I think I've proven that's not necessarily true."

Next Steps

When asked by reporters how he planned to continue his work, Castellucci said he was still considering next steps.

Finally, he sighed:

“I’m still worried about another big brainwallet site popping up. Without cryptocurrency, if you find a bunch of money that you don’t know who owns it, you can hand it over to the police and let them deal with it. But with cryptocurrency, who would do that? What would the legal consequences be? I don’t know.”

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