Methods and associated systems provide secured data transmission over a data network. A security device provides security processing in the data path of a packet network. The device may include at least one network interface to send packets to and receive packets from a data network and at least one cryptographic engine for performing encryption, decryption and/or authentication operations. The device may be configured as an in-line security processor that processes packets that pass through the device as the packets are routed to/from the data network.