I don't want to pick the prize myself, but instead make sure people can be sure it's a random draw and not me giving prizes to whoever I like. I don't know why I care about it but I do.
I have created several tickets, which basically are short pieces of text. e.g.
"kubesolver won the prize"
"cubeshepard won the prize haha"
"someone else won"
I could ask someone in the topic to pick one of these texts, but then it would be their preference and not a random choice. So what I did is that I applied a hashing function sha1 (google it up) to each of those pieces of texts and posted in the topic those hashes.
it's functionally the same as a person selecting a card with a name without being to read what is written on a card.
The hashing function has this property that it's super hard to reverse it. So if I will show now that
Code:
sha1("Batman123 1 ticket for participation. Prize 5)") = e8268
it means that this ticket indeed was for batman as I couldn't on the fly come up with other text that produces the same sha1.
This way the draw is fair unless I didn't collaborate with people drawing.
Now that the contest is over I could publish all texts for hashes if anyone wants to check me.