Abstract: A security system is provided for controlling access to information stored in a target memory in which an access key carries a random access binary memory which is electronically programmable, electronically alterable, directly electronically readable and non-volatile. The memory carried on the key constitutes an integral portion of the target system memory when the key is inserted into a receptacle. The receptacle has a zero insertion force socket to reduce wear and provide direct electrical connection. The key may have an extremely wide variety of coded information programmed into it; when the key is removed from the receptacle, the target system will not operate correctly since a portion of its memory is effectively missing. The system may be retrofitted into existing target systems or incorporated in future target systems.