(3) US5706426 Software protection method and apparatus

US5706426

這也是 software protection的專利，因為我寫了太多種做法，所以 reference的專利倒是很多。

Reference by:

1	7,272,723	SafeNet	USB-compliant personal key with integral input and output devices
2	7,174,466	Sas Validy	Method to protect software against unwanted use with a "detection and coercion" principle
3	7,032,240	Pace	Portable authorization device for authorizing use of protected information and associated method
4	6,848,045	Rainbow	Integrated USB connector for personal token
5	6,671,808	Rainbow	USB-compliant personal key
6	6,317,836	TV Obj	Data and access protection system for computers
7	H1,944	Lucent	Firewall security method and apparatus
8	6,128,741	Rainbow	Compact transparent dongle device
9	5,905,861	Lovell	Data authentication circuit