This episode's headline: High-Tech Censorship. The guests include GEORGE DAVIDA, Cryptographer; DANIEL SCHWARTZ, Former General Counsel, National Security Agency; STEPHEN BRYEN, Defense Department; WILLIAM CAREY, American Association for the Advancement of Science. Byline: In New York: ROBERT MacNEIL, Executive Editor; In Washington: JIM LEHRER, Associate Editor; KENNETH WITTY, Producer; MAURA LERNER, Reporter; MICHAEL SCHREIBMAN, Researcher