Your drawing method is not provably fair. As it is, you could have generated a secret that results in a particularly low MD5 hash for you some name (real or fake), and enter the contest later using an alt account.

I'm not saying that you would do anything so nefarious, but you need some element unknown to you to prove fairness. For example, you could use the hash of the first BTC block that is mined after the contest has officially ended.

That being said, this is a nice contest. Count me in.