Competitive enterprise has lots of secret files in digital form, which is vulnerable to illegal online activity. The authors' target network accepts authorized users on registered machines. In general it is known that the traditional public-key scheme is suitable to strong authentication and encryption, but it is inferior to the IBE (Identity Based Encryption) scheme in terms of performance and certificate management. Thus they improve the WP (Weil Pairing) IBE scheme so as to be suitable to their SFS (Secure File Sharing) system with certificate-less key revocation as normalizing public identity. In addition, the man-in-the-middle attack is negligible because the security is based on hard ECDLP (Elliptic Curve Discrete Logarithm Problem).