Okay that's half the problem. Where do I keep my database of hashes though?

W̶h̶i̶c̶h̶ ̶b̶u̶i̶l̶d̶ ̶s̶y̶s̶t̶e̶m̶s̶ ̶a̶c̶t̶u̶a̶l̶l̶y̶ ̶d̶o̶ ̶t̶h̶i̶s̶?̶ [answered by sibling comment]