There’s no best way to do this. In fact, there must be millions of ways…
I made a little BP here:
What you do is download the text file. Open it and copy the contents, then paste it into the level BP.
You’ll need to right click on some of the greyed out nodes and choose ‘convert to variable’, then it will work.
It goes round in a circle asking for 3 keys and gives you 5 seconds to get them right. The just says ‘Pass’ or ‘Fail’.
It works pretty well but two problems with this are:
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You can hit wrong keys, it doesn’t test that.
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You don’t have to hit them in order.
But you get the idea. Also, in reality, you would show the keys and ask for them using widgets, but that’s another story 
The logic is here…