A method of handling data transmission and reception in device to device communication for a first communication device in a wireless communication system is disclosed. The method comprises connecting to a network of the wireless communication system, using a first ciphering key to cipher a first plurality of data blocks in a communication path corresponding to the second communication device, wherein the communication path is used for transmitting the first plurality of data blocks to the second communication device and is not traversing the network, being configured to release the communication path by the network, and using a second ciphering key different to the first ciphering key to cipher a second plurality of data blocks in a connection corresponding to the network, wherein the second plurality of data blocks include data transmitted to the second communication device.