A method of concealing meaning by replacing words or phrases with other words, numbers or symbols.
The CIA glossary distinguishes a code from a cipher: a code replaces whole words or phrases with other words, numbers or symbols, whereas a cipher works on individual letters. The International Spy Museum also lists the codebook – a dictionary used to convert words into groups of characters and back again.1,2
According to the US Department of Energy, Soviet intelligence cables from the Second World War were enciphered with a one-time pad, which should have made them unreadable; American cryptologists in the VENONA programme read some of them thanks to a procedural error on the Soviet side.3
Sources
- CIA, Spy Speak Glossary
- International Spy Museum (Washington, DC), Language of Espionage (glossary)
- US Department of Energy, Office of History and Heritage Resources, The Manhattan Project: Venona
Checked: 4 November 2026