Topic: What characteristics make a solid brain wallet? (Read 3835 times)

Log₂(200) is ~ 8.

Really long memorable phrase

Well, personally, I don't want to have to trust any computer-based RNGs, and I also don't trust any naive notions regarding which methods for generating/obfuscating a short-ish passphrase are "sufficiently obscure" yet "easy to remember," so instead, I use Diceware to compute a truly random, 10- or 20-word brainwallet passphrase, calculate its Bitcoin address on an offline computer, print everything out in multiple paper copies which are safely hidden away (since I also don't trust any digital media to stay readable), and, for the coldest cold-storage wallets, never, EVER enter the sensitive data (passphrase or private key) into ANY online computer.  If the passphrase is 20 words long (100 die rolls), this method gives you a full 256 bits of entropy, which is as secure as any Bitcoin address can be, but a 20-word phrase is much easier (in a pinch) to memorize, or to read over the phone to someone, than a random string of letters and numbers would be.  My full method is described at:

http://minetopics.blogspot.com/2013/03/ultimate-bitcoin-security.html

One easy trick I use is to take a common phrase you might not forget.
Then replace, in all subsequent words, any occurrence of character appearing in the first word with 'a', 'b', 'c', 'd', etc.

For example:
One must be poor to know the luxury of giving

becomes:
One must ba pbcr td kefw thg luxury hf giviig

Which has >200 entropy and is basically impossible to crack, yet pretty easy to remember (one common phrase+one transformation method).
Of course, the transformation method is up to you, this is just an example, but it needs to remain easy enough.

I just finished migrating data from over 50 CD-Rs that we're all going on 20 years old. They were all OK. FWIW.

Someone watches Person Of Interest .

who would of known knowing 1337 would pay off  

good trick for an easy to remember strong password

I think optical media is only expected to last for 10 years or so before the plastic starts breaking down. Some USB sticks are also only guaranteed to retain their data for 10 years (or less!). It's something to keep in mind if you are going for very long term storage, physically written down/engraved seems to be the safest bet.

I'll take that as a yes then, and I'll make it nine or ten words just to be sure. Or will I?

Cheers.

Really?

Which 2 languages?

The Oxford Dictionary has more than 170,000 words. There are at least 85,000 in the Chinese dictionary.

Assuming we don't know how many words from each language are in use that equals 255,000 ^ 8 or 17,878,000,000,000,000,000,000,000,000,000,000,000,000,000 combinations.

And that's assuming we correctly guessed which two languages are in use.

Ready to get started brute-forcing? 

Yeah for example one of them was o8ZKldMvp9, 14 years ago. I used to use it on a daily basis .



The trick to this is remembering it every single day, as part of some daily routine like washing your teeth for example. At first you'll need to write it down somewhere and read it to remember it but day after day you'll realize that you don't need the paper anymore. Mind you, you need to be religious about it. That's the actually difficult part, not the passphrase in and of itself. Feel free to go for 20 words if you follow this route, you'll memorize them with little effort.

Not anymore, since you've just given the world a hint to your passphrase.

one difficult-to-measure parameter of a brain wallet is how well you are able to remember
the pass phrase. May be you are "pretty sure" to have it right now, but you memory
may not be as good in a year, in 10 years ... Do you remember your passwords from 10 years ago right now?
Of course it's not as much of a problem if it's for a short time.

Eight random words in two different languages should suffice, yeah?

No... Good way to get your btc stolen.

SHA256  a certain page of a book

I agree with this. It's easy to look at the OP's suggestion and say "it's all tropically-themed and the number at the end is easy to guess!", but how would anyone know what to look for without seeing it first?

Could a computer be programmed to brute-force using themed sets? What if the OP threw in a single word that didn't fit the theme--would the computer not guess that combination because it's only looking for themes? What if the number came before the last word?

I believe "try all possible combinations of themed words, of all possible lengths, and then try each possible theme set with a random non-themed word put in, in each position... and try a list of common numbers, of all common lengths, added to each position..." would be just as time consuming as brute-forcing one character at a time.

Sure, it might not have much entropy. But unless two people are relying on RNG's that aren't random and both come up with the same numbers, using low entropy isn't going to make it much easier for someone to brute force your password (if it's long enough). 

Are you sure you will be able to correctly recall the 12 random words from Electrum in, say, 10 years time?

Why not use something you've been already remembering for years?
Say, surnames(or nicknames) of your (girl/boy/best)friends, in chronological order.

There are a lot of surnames, so they have bigger entropy than words from Electrum (unless your friends are all Koreans ), so you don't even need 12 names. Since password attacks are directed not personally at you, but at the whole population, it seems to be quite safe way. And if you keep your private life private, even attack directed personally at you won't be successful.

Don't create your own passphrase. Use electrum and it will make one for you. Memorize that.

If you want to know why creating your own passphrase is a bad idea please see below:

1. Brainwallet used just as deterministic wallet if the entropy source is low or compromised in the working environment. Here it is not necessary that you memorize the passphrase just the unpredictable and high-randomness aspect of the passphrase.
- Generate a random passphrase.
- Take half of the passphrase and intersect the same amount of characters in an unpredictable way.
- Eventually make a hash of it as 3. step and take that hash value as passphrase.
This way will be awoided that you choose some week passphrase and the passphrase generators eventually weekness also.
2. Brainwallet used with human mind memorable passphrase.
- write down your main email address (eventually add your name also) - this part to make hard to bruteforce all passphrases on a global level
- add a random passphrase easy memorable for you - not to short and not in a predictable schema
- stretch it with bcrypt 12 rounds - to limit the brute force attacking speed
Use the obtained hash as input value to generate a keypair or a keypair list or chain.
Newer reuse(at least by a higher BTC amount than 1 BTC on an address) the same address.
It is also recommended to generate the keypairs from your passphrase with an amnesic live OS without internet connection and save only the addresses ona USB stick if you want to use the brainwallet as longterm saving. (If you want to use your coins more actively then you need to import the keys in an encrypted wallet.)
Transfer the amounts on your generated addresses and the wallet(if you imported the keys) from the USB to your active computer .