Related Clues:
- Like many wartime messages
- Having secret marks, maybe
- Like DNA
- Like something written in 21-Across
- Ciphered
- Like cryptograms
- Cryptic
- Like some messages
- Requiring cracking, perhaps
- Impossible to read
- Indecipherable
- Did some programming
- Like wartime messages
- Wrote in Java
- Like some diplomatic communication