***The following is my updated algorithm for determining the lottery winners***
Ok, so this uses your already provably fair method for determining rolls.
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At the start of the round, have the server create a seed, and display that seed hashed to the public on the lottery page. At the end of the round, automatically post an excel spreadsheet to Dropbox (I believe they have an API) showing the acquired tickets for the round and who they belong to (like this:
https://docs.google.com/spreadsheets/d/16FCMiXgVXI9unoFMm2qgCoK7gGA5BaZqth2BCoddT7k/edit?usp=sharing). Posting the file to Dropbox leaves an upload timestamp created by a server INDEPENDENT of freebitco.in, meaning the file cannot be tampered with or it would be evident in the timestamp.
Then, take the next bitcoin block to be generated after the file was posted, and use its hash as a server seed. The nonce is the lottery round number, increasing by 0.1 for each iteration (1st, 2nd, 3rd, etc...). Create a roll number using these three inputs.
Define q by multiplying 10 to the power of the digit count of the total number of tickets and adding the difference between number of digits in the highest possible roll number, and the actual amount of digits in the roll number in zeros - This accounts for low rolls (q = 10
digitCount + (extraZerosAmount = totalPossibleDigits - actualDigitAmount)). Define t by multiplying the roll number by q (t = roll# x q). Define n by taking t and performing a modulo operation with the round's ticket count, and adding one (n = (t%tktcount) + 1). And there you have it, the winning ticket is the nth ticket acquired in the round.
Users can verify the winners after the round by doing the roll formula and checking it against the spreadsheet posted on Dropbox, with the INDEPENDENT upload timestamp by Dropbox servers ensuring that the spreadsheet was not tampered with after the block was generated and roll formula completed.
Let me know if you have any questions, or if I missed anything.
Jake
Edit: This may seem very complicated and jumbled and I apologise in advance, but in my honest opinion this covers every front possible in order to achieve the complete provably fairness of the lottery, and give all users confidence in doing so. If this seems complicated and you don't understand, ask me for an example and I will post one.
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