access
arcanum
authorized
classified
concept
conceptual
confidential
confidentiality
espionage
forbidden
hidden
hush
hushhush
information
insight
insightful
intelligence
paper
penetration
perceive
perception
perceptiveness
perceptivity
perspicacity
privacy
private
privy
protect
protection
restricted
safety
secluded
secrecy
secret
secure
security
spy
text
top secret
torn
under wraps
undercover
underground
undisclosed
unknown
unpublished
unrevealed
visibility
visible
word