Intelligence officials now suspect that, thanks to the alleged spy ring's information, the Soviets became aware of the extent of their missile subs' vulnerability. In addition to shifting its priorities to quieter operations and developing tactics for keeping its biggest undersea vessels in safer waters, Moscow also stepped up efforts aimed at detecting U.S. subs, these officials believe.
In contrast to the major 1975 worldwide Soviet naval maneuvers, called "Okean '75," when Soviet tactics emphasized projecting power into distant waters and cutting Western sea lanes, more recent maneuvers have focused on finding and destroying enemy submarines and protecting their own missile subs--changes that could have been influenced by the alleged Walker revelations.
As a result of the Soviet change of tactics, the role of the American hunter-killer submarines is growing more difficult and more dangerous. And, with the Soviets' giant Typhoon subs no longer making long open-sea patrols, an increasing part of Moscow's missile submarine fleet is less exposed to U.S. attackers.
Intelligence professionals believe the Kremlin may have reaped a second major windfall from the Walkers' access to cryptographic material and coded messages.
The Soviet Union, like the United States, records all electronic signals it picks up and files them all in library-like systems. Both nations also change their codes every day, but the files are kept in hope that past messages someday can be deciphered--offering valuable information about an opponent's tactics, command systems and other matters that would provide a significant advantage in a war.
The clear text of secret messages allegedly passed to them by Walker could be used by the Soviets in this way. Using information about the frequency and other details of the U.S. transmissions, and retrieving coded messages recorded previously, then comparing the clear text with the coded text, the Soviets could break the code for all messages sent on that day.
Communications on that day between the Navy and other U.S. and allied military services, as well as with other U.S. agencies, also would be decipherable once the code was broken.
The Soviets could extract additional information from breaking even one day's code. Knowledge of how the code was constructed, plus data on U.S. cryptographic machines also allegedly provided by the ring, would have given Moscow's code-breakers better chances of cracking U.S. codes used on other days, intelligence sources said.
The code machines in the most sensitive U.S. communications centers (such as the White House Situation Room) are changed regularly, both as precautionary measures and as improved machines and encoding systems become available. But for communication at a tactical level, such as in submarines and at fleet and division headquarters, each service and agency decides if and when to buy new equipment.
The services, including the Navy and Army, often defer new purchases of expensive coding apparatus unless there is evidence that the existing machines have been compromised. The Navy may well have been slow in replacing its older machines, purely for financial reasons. This could explain why it now faces expenditures of "many millions of dollars," as Navy Secretary John F. Lehman Jr. estimated, to buy substitutes for the now-compromised equipment.
At least one more complicating factor is that older coding equipment in service must be able to communicate with newer equipment, and vice versa. This has raised the possibility--highly improbable, experts said, but not impossible--that encryption equipment more sophisticated than the 15-year-old machines available to the Walkers may also have been compromised.
Ripples of apprehension resulted from all these questions last week, including:
--The Army, Marines and Air Force created task forces to study the impact of the Walker case on each service, and the National Security Agency, which makes code machines and encryption systems for all of the government, set up "study groups" to examine repercussions on its activities.
--The Senate Intelligence Committee embarked on a "comprehensive review" of Soviet intelligence activities and U.S. counterintelligence efforts, which will include examination of the broad national security implications of the Walker case. The House Intelligence Committee, after a detailed briefing on the case, focused on remedial steps that have been proposed, including random polygraph lie detector tests.
Meanwhile, intelligence professionals are withholding judgment on how badly U.S. national security has been damaged. Where the Walkers eventually will rank on the scale of sensational espionage cases also still is in doubt.