step 105 the user is inquired whether to end the installation or not if the user confirms the complete of the software installation then the security software is quitted and the installation procedure is ended therefore the installation of the software is fail at step 106 the user is prompted to connect the usb flash memory disk to the usb interface and the process goes to the step 103 after the user confirms the connection at step 107 a password of the usb flash memory disk is inputted by the user at step 108 the operation system log on information and the usb flash memory disk password is formed into an encrypted file at step 109 the password is written into the private bytes or the normal bytes of the usb flash memory disk at step 110 it judges whether the writing of the password is successful or not if it is the process goes to execute the step 111 if it is not the process returns to the step 105 at step 111 the installation of the security software is complete the operation system is rebooted next the flow for authentication while the operation system of a computer is started up will be described with reference of fig4 as shown in fig4 whenever the operating system starts up the security software installed in the computer executes a security authentication to.