To make this raffle fair and make sure that we can't collude with winners we have asked for the help of 2 trusted forum members.
John K will be holding the 100 BTC in escrow until it is paid out to the winners.
dooglus will be holding part of the secret key that will be used to compute the numbers.
Provable fairnessdooglus and we (Coinroll) will generate a secret (20 char alphanumeric) and commit to it by posting its SHA256 hash. We will not know dooglus' secret and vice versa. Everyone will be able to save both hashes in advance and confirm they correspond to the secrets when the raffle is over.
To pick the winners we then reveal the secrets and concatenate them (our secret || dooglus secret) and take the SHA256 hash of the resulting concatenation.
We then take 4 bytes from the hash and convert it to decimal. The winner is the [n + 1]th signature post (all other posts are ignored for the purposes of choosing the winner) where n = picked_number mod total_signature_posts. Since 4 billion is a big number the probability difference of n for various total_signature_posts is insignificant.
We continue doing this for the other winners. When we reach the end of the stream we SHA256 the hex representation of the hash again and continue on the output. If a number gets picked twice then we move to the next number in the stream.
There will not be any changes to the thread in the last 7 days so everyone can verify that the list has not been changed in any way. Once the final review of participants is done 7 days prior to drawing, topic will be moved to the auction subforum, where people can't delete their posts.
Our secret's SHA256 hash is
4b31c376470a57c5a216c52b9c44676f0a22f9aac2e3a95dbe1cd0a0a789313e