Problem with the system i could keep submitting raw hex transactions and keep going for the tx id that I want, and don't broadcast it if its a txid that makes you win. Maybe hash the tx with a secret key, and you provide the sha256 hash of that secret key to verify that you aren't change it. This would make the random number not predictable if you don't know the secret key, which is released at the end of the day (week in this case)
makers sense now.
Fluky will be using the unix timestamp from now.
thanks all.
Thanks for your reply, You say that the unix time stamp can be changed? The value will be taken from the "received time" by blockchain.info that value can't be changed, can it?
Also 00 will win over 01 because the number would be taken from the 3 first digit of the inversed unix time: like 1422265904 = 409. Althought the players could try to get it in the lowest digit it's very easy to fail and get a higher number.
Another option is adding the TXID with the hash of the block-height where it was included then hashed again, that way I think there's no way it can be changed, what do you think?
Btw, while this get sorted out, the round will be increased by 24 hrs.
Btw, we've noticed some other strange transactions.
, it seems a possibility , it looks to me like a cheater, if so, I'll refund that amount to the players that lost fair playing. 
