Lead: For 400 years service men and women have fought to carve out and defend freedom and the civilization we know as America. This series on A Moment in Time is devoted to the memory of those warriors, whose devotion gave, in the words of Lincoln at Gettysburg, the last full measure.

Intro.: A Moment in Time with Dan Roberts.

Content: One of the daunting challenges of modern warfare is insuring that communications remain secure. As code-breaking technology has progressed and skills have grown internationally, intelligence experts who are successful in penetrating command and control networks of their enemies could never be certain that the same thing had not been done to them.