Related Clues:
- System of rules
- System of signals
- Code - 0
- Secret system of letters. words etc
- Cipher — set of principles
- Rule book
- Render unreadable, in a way
- Building inspector's expertise
- Cryptologist's interest
- Be a computer programmer
- Internet expert Lawrence Lessig's subject
- Secret payment at door for ecstasy
- Thing to be cracked
- What the four circled answers 'crack'
- Set of signals for sending messages