Walkers Cold War spying for the Soviets started in 1967, when he was selling information about US Navy communications systems and the encryption codes used to configure Navy communications gear for secure transmissions over the Fleet Broadcasting System. The information he provided, some claim, led directly to the North Korean seizure of the US Navy intelligence collection ship USS Pueblo, as the Soviets apparently spurred the attack to gain access to the hardware used with the material Walker provided just a month earlier.
Back then, crypto codes were printed on cards or sheets of paper. There were single-use pads for transmitting encoded voice communications in the clear over unencrypted circuits, and cards used to configure the switches on crypto gear in the radio room. It was this second category of materials, which had the printed cryptographic keys used with the KW-7 Orestes teletype encryption system, that Walker sold in bulk to the Russiansfirst by stealing them himself, and then by enlisting family members. The cards initially gave the directions for how to manually configure the plugboard in the KW-7, until the Navy moved to a punched card reader in 1977 to configure the daily codes.
As a result, the Soviets were able to record encrypted radio broadcasts from the fleet, and then attempt to match them up after the fact with the crypto keys provided by Walker. It didnt give them immediate real-time insight into fleet operations, but it did give them access after the fact to millions of Top Secret-classified messages over the years. It included access to weapons and sensor data and naval tactics, terrorist threats, and surface, submarine, and airborne training, readiness and tactics," Defense Secretary Caspar Weinberger had said. That data, Weinberger claimed, helped the Soviet Union make huge leaps forward in the development of their own navy.
Its hard to calculate the total damage done by Walker. The data he provided could have contributed to Vietnam wartime deaths; it most certainly escalated the conventional arms race between the Soviet Union and the United States over the last two decades of the Cold War. And it could have led to the exposure of US intelligence assets around the world....