METHOD AND MEANS TO LIMIT ACCESS TO COMPUTER SYSTEMS

摘要

In a preferred embodiment, a method of limiting access to computer systems which method includes scrambling identification card information with time information so that the resulting code can be used for only a limited period of time, thus preventing unauthorized persons from using the code at a later time. In another aspect of the invention, one or more mu -metal shields are embedded in an identification card, thus identifying the card as being valid and also providing means to indicate when a valid card is being removed from a card reader.