Chapter 9 - Design of Real-Time Speech Secure Communication over PSTN

Abstract

This chapter introduces the design and implementation of real-time speech secure communication over PSTN, using the information-hiding-based model and algorithm. This chapter deals with the Speech Information Hiding Telephony (SIHT) system architecture, provides a simulation model, and introduces the method to realize it. SITH sets up a covert communication between two parties whose existence is unknown to a possible eavesdropper, and it can transfer information from one place to another over PSTN securely. SITH changes an ordinary telephone into a secure communication system. The design of SIHT uses one fixed point DSP (TMS320C54x), three floating DSPs (TMS320C31), and a single-chip microcontroller based on an embedding system method. All DSPs work in parallel processing speech encoding, decoding, encryption, decryption, hiding, extracting, bus arbitrary control, and so on. SITH consists of several main functional blocks, including a speech coder and decoder, an encryption and decryption algorithm, a hiding and extraction approach, e-modem, key, liquid display, and smart-card reader circuits. When SITH is connected to a PSTN, the modem communicates at a rate of 33.6 kbps. By using both public key and private key algorithms, SITH provides a safe and secure speech communication between two parties over PSTN.