Quote from: serves-two on November 24, 2013, 06:31:09 AM

Don't. Bad for privacy, usually done wrong and hacked, even if done right people often forget or lose the password...

If you still must create a brainwallet, for the love of $deity_or_lack_thereof please make sure you generate the passphrase genuinely randomly - e.g. an Electrum-esque 12 Diceware words chosen with real dice, written down multiple somewheres (perhaps split up) - and use some kind of KDF that requires a substantial amount of time to slow down brute-forcers anyway.

But, please, just don't even do it in the first place.

I appreciate the good advise. I still want to know what the limits are to the number of characters in a brainwallet passphrase, as well as the limits for the private key encryption passphrase in BIP38.

The passphrase I am thinking of has 230 bits of entropy, and I can recreate it reliably. I was thinking of using that same brainwallet passphrase for both creating the private key as well as for encrypting it. But I've been thinking of using a different (equally high entropy) passphrase for the second step of the process.

So back to my original questions, soes anyone know what the limits are to the size of the passphrases?