Earlier today i made a "birthday card" transaction, encoding a simple OP_RETURN message.
The recipient is a Douglas Adams fan, so on a whim i decided to make the transaction id start with a few 42s – 4242a76834b028a61aa94dcfda878a0106ce0a20d4a3fd9234990b1565b6539a
I have written my own Bitcoin client from scratch, including all the crypto stuff, so that was rather easy to do by adding a counter to k in the ECDSA signing function and letting it brute-force the thing for a few minutes.
However, when all was done i wondered how is something like that usually performed, and a quick google failed to reveal anything even remotely related. There is a bit of speculation about it's possibility on the Bitcoin forum, and that's it.
So, the question is – have anyone ever made a "vanity" txid before?
Is there any meaningful demand for a tool that can do this?