Patent ID: 8701207

Claim:
A method for protecting software on a terminal device by using a security device, the method comprises: providing the security device including a clock which is powered up by a battery only if the security device receives a predetermined service instruction from the terminal device wherein if the clock is not powered up by the battery, the clock does not start counting time; if the clock is powered up by the battery, the clock starts counting time; connecting the security device, in which time limit information limits using time of the security device is stored, to the terminal device; sending, by a protected software stored in the terminal device, the predetermined service instruction to the security device; and receiving, by the security device, the predetermined service instruction and determining whether the clock inside the security device is activated; if the clock is not activated, activating the clock, reading a current time of the clock and determining whether the current time is valid by the security device; if the current time is valid, executing the predetermined service instruction and returning an executing result to the terminal device by the security device; if the current time is not valid, returning a false result to the terminal device by the security device; if the clock is activated, reading the current time of the clock and determining whether the current time is valid by the security device; if the current time is valid, executing the predetermined service instruction and returning an executing result to the terminal device by the security device; and if the current time is not valid, returning the false result to the terminal device by the security device, whereby the software being protected by the security device when the security device sends the false result to the terminal device; wherein activating the clock by the security device comprises connecting, by the security device, a clock chip of the clock with battery, controlling, by the security device, a clock oscillator of the clock to make the clock to start working, enabling a power-off pin and making the clock starting counting time and modifying activation flag of the clock to be activated.