Vanity WIFs ;-)
I know some people may use my WifSolverCuda as a "cracker" for their manually generated WIFs. You may for example remember that you wanted to have "5JVeryConfusedxxxxxxxxPersonWithDementiaAndBackPain" and all you need is to find 8 unknown characters which would produce the correct WIF.
That's a terrible idea. If the private key isn't random, it can be brute-forced much easier.
It goes off-topic but when I think about it, I think it is not worst than brain wallet. At the end, what we receive from brain wallet is not "random" too. And knowing part of brainwallet we may try to brute-force the rest. At the end in one case we talk about sha256 and in other case as a base58 decoding.
The idea behind Vanity WIF (do not blame me, I have never did that personally, I was just contacted by some people who use my program to generate that WIFs) is to be able to remember WIF partially, knowing that it is technically possible to restore the missing part. That way we may have known "human readable" part (date, sentence, etc). and have part which is calculated by program, looking for a correct (importable) WIf. Of course one may decide to do extra steps, like prepare WIF in uncompressed form, extract private key and then use it in compressed form - but it is an extra complication, which could cause other problems ("I forgot how I did that 5 years ago").
As a Post Scriptum I may add that we all are humans, years of evolution caused we have ability to find patterns. We may say one text "is random" while other is not. We may say that WIF cannot contain the same characters repeated 10 times, because we
feel it is unnatural. But the chance for that is exactly like the chance for any other combination. Additionally, let's do not forget about different languages. English words has no meaning in Dutch or Spanish and vice versa. Random letters would mean nothing for me, but they could be a "Hello World" in Chinese.
Like they say, if you take many monkeys and they will press random typewriter keys for a long enough, one of them will finally write the whole "Hamlet".
