APPARATUS AND METHOD FOR PERFORMING AND CONTROLLING ENCRYPTION/DECRYPTION FOR DATA TO BE TRANSMITTED ON LOCAL AREA NETWORK

A communication controller for performing data encryption and data decryptio n of data communication packages to be transferred in a network (such as LAN: Local Area Network, or a WAN: Wide Area Network). The data communication package contains a first section of non-encrypted data and a second section of encrypted data. The communication controller comprises a session key LUT uni t (186), and a transmission and encryption section, which includes a data read transmission control unit (102), a data compressing unit (118), a data encryption unit (126), an integrity check value calculation unit (122) constituting a first series configuration, a network transmission controller (134), and a first switch means (108) enabling switching between two modes o f operation a first mode of operation providing bypassing or disabling of the first series configuration and enabling communication between the data read transmission control unit (102) and the network transmission controller (134 ) for transferring the input data directly hereto and a second mode of operati on enabling communication between the data read transmission control unit (102) through the first series configuration to the network transmission controlle r (134).