|
April 02, 2013, 07:49:51 AM |
|
While the risk of someone coming up with the same key is significant, the real danger is that a brain wallet is much easier to crack than a random bitcoin address. A typical desktop computer can generate and check a million keys a second.
For example, some number of people in the world will use obscure phrases from Shakespeare to create their keys. The complete works of Shakespeare consists of about 900,000 words, so there are about 9 million possible phrases of 1 to 10 words. Their money will be stolen in 9 seconds.
Some people will use their home address to generate the key. Assuming that there are maybe 200 million home addresses in the U.S., it will take about three minutes to steal all of their money.
What about a key made from 5 random words? Well, first of all, the words won't be completely random because they must be memorable. Most people will probably chose from a list of less than 1000 words. That's 1,000,000,000,000,000 possible 5-word phrases. That's a huge number, but at 1 million keys per second, the entire list of 5-word phrases can be searched in 31 years by a single computer, or 11 days by a botnet of 1000 computers. If this is how you generate your brain wallet, consider your money stolen.
|