This document specifies requirements for high security locks (HSL) for reliability, resistance to burglary and unauthorized opening with methods of testing. It also provides a scheme for classifying HSL in accordance with their assessed resistance to burglary and unauthorized opening. It applies to mechanical and electronic HSL. For electronic locks used in a distributed system, see prEN 17646 for further information. The following features can be included as optional subjects but they are not mandatory: a) recognized code for preventing code altering and/or enabling/disabling parallel codes; b) recognized code for disabling time set up; c) integration of alarm components or functions; d) remote control duties; e) resistance to attacks with acids; f) resistance to X-rays; g) resistance to explosives; h) time functions.