Possible Clues:

• Protect from a cyberattack, say
• Secure, as information
• Maybe turn to Morse and co to crack Edwardian detective's cases
• Protect, in a way
• Create cryptograms
• Try to make undecipherable
• Put in a secret language
• Make unreadable to the enemy
• Obfuscate, in a way
• Write in Playfair, e.g.