Ok, i must confess that is true for the first bet of a series and i will implement the seed-hash display in advance... but that still does not make a difference for the choice of the hashing algorithm for this purpose
/Sigh. It really does. Just use sha256 and we can all be happy.
Most dice sites use hashes in two distinct ways:
1) to prove to you that they picked your server seed before you picked your client seed and didn't change it after
2) to generate the roll from the seeds and the nonce
It seems this site isn't doing (1) at all. It is (1) that needs a secure hash, because otherwise they can find a pair of server seeds with the same weak hash, show you the weak hash, and only after your first roll do they need to decide which of the two to use.
The hash used in (2) isn't so important - it doesn't need to be secure against collisions at all. Just so long as it gives unpredictable output if you only know part of the input.
As for all the talk about finding hash collisions (in (2)), you seem to be missing the point. In order for this site to cheat, they don't need to find two things that hash to the same long output. They only need to find two things which generate the same roll, which is a 1-in-10000 chance, and so much easier than finding a true hash collision. So on my first roll, the site can literally pick any server seed they like and make me lose. On my 2nd roll, they need to test an average of 10,000 server seeds to find one that gives the same 1st roll, and so will just a 100k hashes they can expect to find a server seed that makes me lose my 2nd bet as well.
For the 3rd bet it's harder, because there's only a 1 in 10^8 chance of finding a server seed which gives me the first two rolls I've already seen, and so the site will need to so around 200 million hashes to have a good chance of making me lose my 3rd 50% bet.
(and it gets 10^4 times harder each following roll - so players should roll 10 times for dust before playing "for real")
I guess I'm just repeating what Eric said, and to which you replied "I have no idea what you are talking about". Maybe I've put it in a way that you can understand?
