New blog post: Hiding Bitcoins in Your Brain

[dooglus]

To make a truly secure brainwallet passphrase take the output of

Code:

dd bs=32 count=1 if=/dev/random | hexdump -e '"%x"'

and convert it to PGP words

That hexdump format drops leading zeros, so you don't always get the same length output.  Use %08x instead:

Code:

$ for i in . . .; do dd bs=32 count=1 if=/dev/random 2>/dev/null | hexdump -e '"%x"'; echo; done
16a1e01aab6de7fe6e8e5e8f28420f0d8cf1d12256321054f57f6973b6e6b2
23db86401bea1e3ac5c089fa1a5333f2403448314a15e3d724995a328e31bee6
e8dbc73fcab648562843757bf32ce6a5ee685689e40a6818ed65f3c1623a00e
$ for i in . . .; do dd bs=32 count=1 if=/dev/random 2>/dev/null | hexdump -e '"%08x"'; echo; done
3e2b8050eba7507b02f8e92e4d046f2e8b77b37914eb33a190bbaec26e589e0b
140b7e3f8ec3d995b8c84c79a1aad8dae792a7da13bbb457432c1543440237a3
ea6ca2eb010fbd8044ea907398308bb4643f23114f5c935162736623cdec6f94

Also note that /dev/random won't always have 32 bytes of random data available, so you might get a much shorter output.

[justusranvier]

Also note that /dev/random won't always have 32 bytes of random data available, so you might get a much shorter output.

It should block until it has enough data.

[thezerg]

It would be unfortunate to make brainwallets inconvenient to generate because they won't hold coins securely for decades when some people may desperately need them for just a few hours or days during periods of travel or social unrest...

[ErebusBat]

OR.. OR....  use a random wallet and store the private key / recovery code in LastPass or keepass.

I understand the 'attractiveness' of brainwallets is that your computer could go away and you can still get your bitcoins back.

HOWEVER usb drives / paper wallets / safe deposit boxes / mom's houses are very effective and cheap. 

This reminds me of a conversation we had at work.  We currently backup on-site and ti our data center, which happens to be about two blocks away from us.  We had the opportunity to add another city to that list.  Whilst discussing it I brought up the good question "if our building is destroyed AND the datacenter is destroyed will we still be in business?"

if you PGP encrypt your wallet and give your mom a copy and put a copy in your safe deposit box and all those are destroyed then most likely your primary concern is going to be running from zombies and not where your magic internet money went.

Just Sayin.

[ErebusBat]

For those of you, who have spare unneeded coins
I have new toy in Google Go :

https://bitbucket.org/mmanchaild/brainqeyz.git

This SAVING brainwallet generator has
some quite secure properties.

On average PC EVERY brute-force attempt of a passphrase will take ~ 90 minutes to perform.
It comes with a cost: application will
 run about 2..3 hours for one launch.
You will need to launch it at least 2 times
(or MORE) for safety reasons.
And then you must compare results.
They must be the same.
 
 

I am interested in how you calculated that every brute force attempt would take 2.5 hours.

[casascius]

A brainwallet generator that has an option that can be cranked up to 90+ minutes might be useful.  But one that requires people to wait 90 minutes to do their first brainwallet, is one that probably hasn't been properly thought through.

A 90-minute or 900-minute brainwallet has useful properties from the perspective of robbery/duress prevention.  Teaching someone that a brainwallet is something that requires at least 90 minutes to access, on the other hand, is going to sound ridiculous.

[ErebusBat]

I am not sure I see the point in this vs truly random keys?

My thought behind brainwallets were so that they could not be lost or destroyed?  The idea behind just using a simple SHA256 was that it was not complicated or hard, you can even find (non bitcoin) related sites to do it for you.

If you require a special program to generate your address then does that leave the realm of brainwallet and enter the realm of super-duper wallet generator?

Don't get me wrong, I really like the idea, but it would be very hard for me to loose anything digital.  But for your average user I am not so sure?

[Dabs]

How about a SHA256 hash of a picture or video from your own camera? The photo or video is of the sky, or of the ground, or something weird; something no one else is going to take a picture of; in the dark, with highest ISO speed for grainiest photo. Or a bunch of photos. Of course, add salt and iterate a few hundred times.

[aliaser]

For those of you, who have spare unneeded coins
I have new toy in Google Go :

https://bitbucket.org/mmanchaild/brainqeyz.git

404, do you have a working link of the souce code?