I don't think you understand what a rainbow table is.

Somebody generated the exact same brainwallet you did, long before you ever thought of using that passphrase.

They've actually generated millions of brainwallets, and they're just waiting for someone naive enough to use the same weak passprases and deposit money into one of their addresses.

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Another thing you can do is repeat hash hundreds and hundred of times. And use a salt - with the original phrase and added to each hash. You can even have a simple formula that changes the salt each hash.

57899@##$% as me salt.
"I like big butts" as my passphrase.

Each hash I change the salt according to the number performed and add it to the previous hash, changing the salt so it grows each time, resulting in a huge salt by last hash.

Reapeat, say, 722 times.

All I have to remember is the salt (write it down), the pass phrase, and the algorythm I used to alter the salt each iteration.
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