“Codes have always been primary espionage targets, but they have become more valuable as encryption programs have become both more common and more complex. Today, even the National Security Agency, the nation’s code-making and -breaking arm and its largest intelligence agency, has trouble keeping up with the flood of messages it intercepts. When decrypting other countries’ codes is so difficult, the most obvious solution is to steal them.”
Source: The CIA Burglar Who Went Rogue | History & Archaeology | Smithsonian Magazine