In this Article, Patterson discusses how the government might introduce deciphered encrypted information into evidence without being forced to expose sources or methods of deciphering.  Patterson proposes a “key theory” where the government would only need to provide a key to decipher the information to the court but not have to reveal how the key was obtained or how it works.  He describes the historic methods of encryption and the problems associated with introducing such evidence in the context of a specific espionage case.  Patterson then describes applicable rules of evidence and how the key theory works within them.