So in the past, if Santa came to a house without a chimney, he would use his magic to create one, temporarily, for the house. This would allow him to come into your home to deliver the presents. But this approach has some issues; it takes a lot of energy to create the chimney, and he's still got to squeeze through it. Plus, it brings dust and soot into the house; this increases Santa's clean up time as he departs.
So bring on the magic keys - Santa's magic can sense these key inside a home, and bring them to him. It allows him to open a door instead; so much easier and so much less soot through the house. The reindeer like it better too; they get a bit tired of having carrots covered in soot when Santa brings them back. It's just better all round!
And don't worry about security. The key remains inside your home except for the brief time when Santa needs it.
"Item arrived as described thank you"