Code we selected was commonest commercial codebook, used both on Terra and in Luna for commercial dispatches. But we worked it over. Prof and Mike spent hours discussing what information Party might wish to send to its agent on Terra, or receive from agent, then Mike put his vast information to work and came up with new set of meanings for codebook, ones that could say "Buy Thai rice futures" as easily as "Run for life; they’ve caught us." Or anything, as cipher signals were buried in it to permit anything to be said that had not been anticipated.