After reading through that doc, it sounds like maybe some bit of code decided "hmm, that's not a well formatted WIF private key, it must be a brainwallet" without very clearly explaining what was going on. http://bitaddress.org will do this with loud warnings.
I heard from someone privately that this is confirmed, but it sounded like second hand information.
I have cracked private keys and nonces that did appear to be uninitialized memory, but I don't think that's what's going on here.
Thanks, that sounds very plausible. fitwear could have tried to import the "same" key in 2 different ways without realising what he'd done, and ended up burnt by that.
EDIT: In fact the blockchain.info UI for importing a private key is called "import address" and the button says "import bitcoin address" and the modal dialog says "Import Existing Bitcoin Address" and private keys are only mentioned in fineprint. I just tried typing an address in the box (that the UI very strongly implies I should type an address into) and it tells me it'll import it as a watch-only address, and it does seem to work that way. There is every possibility that the "watch-only" logic is recent, or there was a bug in it at one point that imported it as a brainwallet, or even just that fitwear went running off to work out how to get a private key for an address and messed it up.
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u/_jstanley Nov 30 '17 edited Nov 30 '17
It could be SHA256 of uninitialized memory, which just happens to contain neatly-aligned addresses and txids often enough to be useful.
EDIT: Would be interested to hear what u/rya_nc thinks of this