Abstract: A locking system includes a tamper-resistant lock and key. The tamper-resistant lock can include a cylindrical lock body with an upper portion having an engagement surface defining a pattern of engagement features, a housing, and a hidden component sized and shaped to fit within the housing that includes an internal lock base into which the cylindrical lock body fastens and a padlock pin configured to secure the internal lock base to a hasp or staple. The key operable for use with the tamper-resistant lock can include a cylindrical key body defining an engagement cavity configured to receive the engagement surface of the cylindrical lock body, a set of complementary engagement features, a plurality of retractable engagement members, and a retractable collar at least partially covering the cylindrical key body.