High-security keys serve two purposes. First, high security locks are extremely difficult to pick. And second, their key profiles are restricted to locksmiths with a contract, meaning that the keys cannot be duplicated by anyone but the contracted locksmith.
Fitch Locksmith has contracts with three different restricted keyways, two of which which are high security. There are other key profiles, while not restricted, are available only to locksmiths, which means unauthorized people can’t take your key just anywhere to get it copied.