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Jon Matonis Contributor


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Brainwallet: The Ultimate in Mobile Money

For as much as I am fascinated by the societal and political implications of bitcoin, I must admit that I am equally fascinated by the implications of Brainwallet. Quite simply, a brainwallet, or thoughtcoin, refers to the concept of storing bitcoin in one’s own mind by memorization of a special and unpredictable phrase. No, you are not actually storing the bitcoin in your mind but you are storing the access mechanism, or seed, to your stash’s private key.

For example, the phrase must be sufficiently long (12 words or more) to prevent a brute force guessing attack, such as “I went seeking freedom, but all the world’s islands were already taken.” It is further suggested not to use a simple phrase or a phrase taken from existing literature because it is more likely to be hacked by a computer that systematically attempts all phrases, similar to a dictionary attack. You want a high level of word entropy. Seemingly random modifications of the phrase would aid in strengthening brainwallet, such as “I went seeking freeeedom, but all the world’s issslands were alreaDy taken.” These simple changes make the entire phrase very difficult to predict.

Next, the phrase itself without the quotation marks is turned into a 256-bit private key with a hashing or key derivation algorithm. Completing this process turns my secret phrase into the 64-character hexadecimal key shown below (this should be kept secret also):


You are basically creating your own public Bitcoin address by personally determining the private key and that single instance is sufficient for our brainwallet. With larger deterministic wallets, multiple public/private key pairs are generated using a ‘root key’ derived from a starting seed and a ‘chaincode’, thus allowing a continual creation of different key pairs based on the same root node. So the final step in our process is to use this hexadecimal key to compute a standard bitcoin address with a utility such as one provided by Casascius or Electrum. Additionally, you can perform this function on bitaddress, a JavaScript client-side bitcoin wallet generator, and even run a stored version locally on an offline computer for security. The testing-only site is Bitcoin Tools. I add the serious disclaimers that hashing/address generation should not be performed online and, although possible, the importation of private keys is not yet standard functionality on most bitcoin clients. Given that, my hexadecimal key computes into the following base58 Bitcoin address:


Now, you are ready to receive bitcoin from anywhere in the world and have the peace of mind that the corresponding private key to unlock, access, and transfer those bitcoin resides solely in your brain. If you forget the phrase or if you die suddenly, the bitcoin is lost and unrecoverable just like if you had burned cash. You can even memorize multiple phrases for multiple accounts, like casual spending and nest egg savings. Why is this so profound?

For starters, it represents the ultimate in mobile money. You have complete financial privacy and asset protection combined with the ability to have those assets fully accessible from anywhere in the world provided there is Internet connectivity or a telephone. You are also protected from theft or confiscation unless a legal jurisdiction can force you to reveal your bitcoin private key that isn’t even known to exist. Possible applications include revealing the secret phrase to a loved one for inheritance reasons or even splitting the phrase into segments with each family member possessing a portion of the total phrase. Off-grid transactions are also possible by simply conveying the phrase via voice or encrypted email. It would also be possible to send bitcoin immediately to someone without an existing address because one could easily be created based on a selected phrase.

It may be awhile before this practice is commonplace since most people do not use bitcoin on a regular basis and most of those do not generate deterministic keys holding $1 million. But, it sure beats lugging around 17 kilos of gold bullion.

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  • I’m surprised Forbes hasn’t covered the Predictinator ( http://caspar.adterrasperaspera.com/predictinator/ )

  • Alan Alan 3 years ago

    This is precisely the way SpiderOak works for keeping your backup & synced data private. You have to remember the passphase to have access to your data.

  • anotonyjohn anotonyjohn 3 years ago

    The Ultimate in Mobile Money.Must people are using mobile.

  • Bruce Upbin Bruce Upbin, Forbes Staff 3 years ago

    This idea blew my mind. I guess fortune favors the young in this cryptocurrency scheme. Like a lot of “slightly older” people, I would never be able to remember such lengthy strings and would probably find myself out of money.

  • Jim Jim 3 years ago

    There are many ways to store your bitcoin wallet and access it online. Braincoin, or thoughtcoin, is just one of the many ways. It may not be the most convenient way but it can have a purpose.

    I believe that the best use of braincoin is for legislative purposes to prove that bitcoin is unstoppable. For example, if the government made it illegal to carry a bitcoin “wallat.dat” file across borders, or if the government made it illegal to encrypt wallat.dat files and send it to yourself to be used outside the country then the way around it would be to use “thought” to carry your bitcoins. The government cannot stop people from thinking.

    This is another reason why bitcoins cannot fail or die.

  • Camron Fox Camron Fox 3 years ago

    Bitcoins started out at a few cents in Nov 2011 and spiked up to ~ $33 each in June 2012 after a CNN special. If you want to trade just a little bit of money the market is fairly predictable and the community is a-lot of fun.

    If you have some ATI GPU hardware you can introduce more bitcoins into the market by selling them or waiting for a higher price. If you have some free CPU time you can mine another crypto-currency called litecoin and sell or trade in the markets.

  • Jacob Jacob 2 years ago

    Regarding Jim’s comment about the invincibility of Bitcoin:
    Matonis mentioned “unless a legal jurisdiction can force you to reveal your bitcoin private key that isn’t even known to exist”.

    Unfortunately, Key disclosure legislation in the UK and case law in the United States mean that a person can be forced to divulge encryption keys or passwords under threat of criminal penalty (including prison time), if the police have /any evidence that the person in question has that information/, and probable cause that obtaining that data would help to prosecute a crime. Having overheard a telephone conversation mentioning that a person has a bitcoin account is in the US considered sufficient to show that he/she knows the key. The right to privacy of thought and the right against self-incrimination (Amendment 5 in the US) no longer hold in this case. See http://www.forbes.com/sites/jonmatonis/2012/09/12/key-disclosure-laws-can-be-used-to-confiscate-bitcoin-assets/, with links to the relevant UK and US (case) laws.

    I am not a lawyer and this does not constitute legal advice.

    Also, regarding “accessible from anywhere in the world provided there is Internet connectivity or a telephone [and hence] protected from theft or confiscation”. The weakest link in this procedure is the moment of entry of the passphrase into an electronic device, be it computer or telephone. If you are not using your own machine, you are subject to taps, hardware or software keyloggers, etc. Use a trusted machine.

    Long live bitcoin!

  • Brings a whole new meaning to the concept of smuggling money across the border…

    Also, if you’re holding a really high-value brain wallet it’s also good advice to stick to offline transactions for sending bitcoins; I wrote a little more on that subject in my Bitcoin brain wallet article here http://bitcoinmagazine.net/brain-wallets-the-what-and-the-how/

  • James Douglas James Douglas 2 years ago

    Vitalik have you seen the site http://www.tradebitcoin.com ?

  • Andrew Stover Andrew Stover 2 years ago

    I figure if the Star Trek Captains can remember all of their security and access codes, we can remember a simple brain wallet code. ;)