Spycraft - Melton [253]
The one-way voice link described a covert communication system that transmitted messages to an agent’s unmodified shortwave radio using the high-frequency shortwave bands between 3 and 30 MHz at a predetermined time, date, and frequency contained in their communications plan. The transmissions were contained in a series of repeated random number sequences and could only be deciphered using the agent’s one-time pad. If proper tradecraft was practiced and instructions were precisely followed, an OWVL transmission was considered unbreakable. The agent was able to use OWVL only to receive communications, but it had many advantages over secret writing or agent meetings. OWVL required no spy gear except a one-time pad, was generally reliable and repeatable, and precluded surveillance. As long as the agent’s cover could justify possessing a shortwave radio and he was not under technical surveillance, high-frequency OWVL was a secure and preferred system for the CIA during the Cold War.43
The OWVL transmission consisted of a series of numbers, usually in groups of four or five. During the 1950s and 1960s, they were read by a man or woman, and in later years produced by an electronically generated voice.44 The numbers could be spoken in any language, usually timed to begin on the hour, quarter hour, or half hour, and were repeated hours or days later on the same or a different frequency.45
Facilities with giant antenna farms to broadcast OWVL signals to every country of operational interest were positioned at strategic locations in the United States and abroad. The sites served the dual purpose of handling CIA staff communications traffic as well messages for agents.
In the late 1970s, OTS and the Office of Communications began upgrading the OWVL system with the development of the interim one-way link (IOWL). This used the same broadcast stations and network as OWVL, but the agent’s commercial shortwave radio was replaced by a dedicated IOWL receiver. The self-contained miniature piece of spy gear was a black box about the size of a pack of cigarettes and half as deep, including the internal battery. Its size made concealment relatively easy and it could be plugged into a standard speaker or operated with headphones. The primary benefit to the agent was the speed of receiving a message; the numbers were transmitted at higher speeds and then stored internally in the receiver to be recalled later. Decreasing the time an agent had to spend performing the covert activity of listening to and transcribing shortwave transmissions improved security and his efficiency; messages that previously had required the agent to listen and copy for an hour could be received in ten minutes. IOWL required the agent to possess and hide another piece of spy gear, but because it was technically equal to OWVL and offered advances in reception speed and an improvement in weak-signal reception, the system was widely deployed.
Short-range agent communications, known as SRAC systems, represented a technological revolution for covcom when OTS deployed the first units to agents inside the Soviet Union in the mid-1970s. SRAC enabled the agent and case officer to exchange information without being required to come into close proximity, or conduct a clandestine act such as loading a drop that might be observed. It also eliminated the risk of leaving sensitive material unattended in a dead drop, which might be discovered and traced back to the agent.
The original SRAC systems exchanged short-duration, encrypted radio-frequency messages of a few hundred characters in less