A communication controller for performing data encryption and data decryption 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 unit (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 of 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 operation enabling communication between the data read transmission control unit (102) through the first series configuration to the network transmission controller (134).