Security of computer communication

Security of digital computer communications is rising on the list of computer security requirements as the interconnection of computers becomes more commonplace. The reasons for interconnecting computers include improved service, improved reliability, and improved information. However, there are risks in connecting computers. A recent newspaper article reports a story about a woman who was told that she could not make a deposit in her bank account on a certain day from a branch bank. When she asked why, the answer was “because its raining too hard.” The reply was absolut.ely accurate. When the intensity of the rain exceeded some threshold, the communications between the terminal in .the branch bank and the computer in the central bank became garbled because of wet telephone connections and all interbank operations had to be suspended. The security provided by the techniques described in this paper will do nothing to alleviate this problem. In fact, the techniques cannot solve many of the practical security problems encountered in computer operations. They will provide, however, high levels of security against certain types of real threats, both existing and