A primer on cryptography in communications

The secure transport of messages was the concern of many early civilizations. Since then, different methods have been developed to assure that only the sender and the addressee would be able to read a message, while it would be illegible or without significant meaning to a third party. Today, this practice continues with more fervor. Wireless, wired, and optical communication networks are able to transport unimaginable amounts of data and thus privacy of information and security of the network are of the utmost concern because a good part of the transported information may be very sensitive and/or confidential. Confidentiality of information has been particularly popularized with the explosive growth of the Internet, which has touched most people's lives. However, from the outset, the Internet was based on open network architecture with computer-based nodes and without network security, and thus was vulnerable to attackers and hackers. Wireless networks transmit in unguarded space and thus are also subject to malicious actors. Dense wavelength-division multiplexing (DWDM) optical networks transport a massive aggregate traffic that has exceeded terabits per second per single fiber; therefore, the issues of information privacy and network security are equally important. As a result, the development of unbreakable cipher keys, cipher-key distribution, identification of malicious actors, source authentication, physical-link signature identification, countermeasures, and so forth has been the major thrust of research efforts with regard to cyber-security. This article focuses on cryptography, and is the first of a series of three articles on cryptography and security in communications. Subsequent articles will cover wireless and IP network security, as well as optical network security, quantum cryptography, and quantum-key distribution processes specific to optical networks.