Related Clues:

• Make secret
• Make hard to read
• Protect, in a way
• Put into code
• Cipher
• Protect from spies, in a way
• Code
• Put into cipher
• Make secret, in a way
• Encipher
• Convert ordinary language into code
• Convert into code
• Change into coded version
• Make unfathomable
• Code to open half an underground vault