A cryptographic device and method are disclosed for processing different levels of classified information. Input and output ports are physically isolated on the cryptographic device. Within the cryptographic device, each port has its packets labeled in such a way that it can be processed differently from other packets by a cryptographic module. High-assurance techniques are used to assure labeling and proper processing of the packets. These labeled packets are intermixed on common pathways regardless of level of classification. Despite intermixing, separation of the packets is assured through the process.