Locking system and locking method

A locking system comprising:

• a portable device having a public code comprising,
• first storage means for storing a first authentication code,
• a first control section for generating a rolling value and for creating an ID code by using said rolling value and said first authentication code, and
• transmitting means for transmitting said ID code;
• a management server for managing said computer;
• and
• a computer comprises,
• second storage means for storing a second authentication code,
• receiving means for receiving said ID code, and
• second control means for recovering said rolling value and said first authentication code from said ID code, creating a spare code by using said second authentication code and said recovered rolling value, and storing said spare code, and wherein
• said second control means unlocks said computer when said recovered first authentication code matches said second authentication code, but locks said computer when said recovered first authentication code does not match said second authentication code,
• when said computer has been locked, said second control means unlocks said computer when a code that matches said spare code is input, and
• said second control means creates a rolling code using said public code and said rolling value in order to acquire said code that matches said spare code from said computer management server.