Read the excerpt from the code book. although traffic analysis, tempest attacks, viruses and trojan horses are all useful techniques for gathering information, cryptanalysts realize that their real goal is to find a way of cracking the rsa cipher, the cornerstone of modern encryption. the rsa cipher is used to protect the most important military, diplomatic, commercial and criminal communications—exactly the messages that intelligence gathering organizations want to decipher. if they are to challenge strong rsa encryption, cryptanalysts will need to make a major theoretical or technological breakthrough. what is the central idea of this paragraph?