Related Clues:

• Unreadable
• 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
• Did some programming
• Like wartime messages
• Wrote in Java
• Needing deciphering
• Encrypted