Check the Steam id of a buyer

How can I get the steam id and their srepective steam emails of all the users of my game.
For example what i want is that I get the name,email of all the users who have downloaded my game from steam.
And then use that for authentication of some kind.
Is that even possible?

Hello there,

this question is in no way related to Unity so this is somewhat unfitting in this forum…

Don’t want to be a d*** about it so here goes a thought on this: Judging from your question you either do not have the steam source sdk integrated into your game yet or did not fully understand what you do with it.
Then again from the “piracy” tag you put on the question you apparently are afraid that people will get around buying your game. For this you have to put in some more information. Is it an offline game? In that case you will never be able to make your game crack-proof. There is always a way. This is the reason why bigger companies use more and more “live-service” for games. Though not even that is fool proof.
If your game is a multiplayer game you should provide more insight into what you actually do.

Actually my game is offline. But I can make a login system
for it and is there any way to make piravy difficult. I know it is kind of impossible to make soemthing foolproof from piracy but at least we can make it hard so that not every peep here and there can steal the game.