Remove brainwallets from site

[dabura667]

Maybe replace with BIP39 / A tool that can generate offline transactions for brainwallets without showing the address / WIF private key to the user.

All tools that show the user a WIF private key and Address in response to a passphrase with a single SHA256 algorithm with 0 key stretching is just asking for people to lose money.

I understand this is a key functionality of your site that is one of the main functions people use it for, but that is also the presentation at DEFCON has served as a well needed wakeup call for people relying on bad brainwallets.

Alternative solutions:

1. Implement stringent password requirements that will search input for common dictionary words / simple replacements of letters with symbols (s > $; a > @) and outright REFUSE INPUT if not met.
2. Implement strong key stretching.

As for backwards compatibility, you could make some tool to aide in recovery.
(like https://bip32jp.github.io/english/recoverbrainwallet.html )

Thanks for the consideration.

(The pull request was more symbolic than anything, so I might have missed some stuff to delete/fix)

[pointbiz]

Using SHA256 to make a Bitcoin Private Key has been around for a long time and people were doing it before it was available on my site. People requested this functionality and doing the SHA256 on my site can help people avoid needing another tool to accomplish their objective. However, your pull request leaves the ability to do the SHA26(passphrase) on the wallet details tab which was the first place I put this functionality because I didn't want to make it easy (then people kept asking for it cause they didn't know it was buried in this way).

At some point in time the idea of "SHA256(entropy)" turned into "SHA256(brain_entropy)" and the meme Brain Wallet was created. I'm not a fan of Brain Wallets and you could easily call the Brain Wallet a "Deterministic Wallet". This was a defacto standard before BIP32/39 came along.

I have plans to add BIP32/39 support. I'd like to provide a few different random number generator options with at least one that guides you through providing physical randomness (like dice rolls) and combine this with BIP32/39. When that overhaul is accomplished it will make more sense at that time to do the removal suggested here.