Related Clues:

• Cryptographer's study
• Sets of laws
• Makes unreadable, in a way
• Message systems
• Features of secret messages
• Conceals from the enemy, in a way
• Makes secret
• They're no good if broken
• Encryptions
• Secret languages
• Does cryptography
• Protocols
• Hides from the enemy, say
• Protects from the enemy, in a way
• Cryptanalyst's concerns