A multi crypto lottery project.
We're a group attempting this very project, launching in a few days time. Watch
https://8bet.io to see how it goes.
... the winnings are transferred to the purse from which the ticket was purchased.
This part isn't as simple as it sounds - as you can't really "send back" to the address that funds were received from. This has been discussed quite a bit on this forum.
How will you ensure that the lottery happens fair...
If you're interested in how we achieve this, see our blog posts on 8Bet:
https://8bet.io/blog/how-it-all-works/