The need for undercover parties to communicate with each other is the Achilles’ heel of clandestine operations. As discussed in the earlier manual section on electronics, it is difficult to prevent communications falling into the hands of a determined enemy. As a secondary defense, messages are often sent in code to foil an enemy’s interception. The science of codes and breaking codes has come along way since ix-nay o-nay hat-tay. The advent of supercomputers allows the code breaker to try uncountable numbers of permutations when looking for the key that cracks a code. The United States uses one-time-use code books for its most sensitive messages and these codes are thought to be unbreakable. But resources needed to develop and use these codes are available to major nations.
The average criminals and terrorists rely on much simpler codes or substitute words to disguise their real conversation. In these cases their secret communications are often read.