Related Clues:

• One if by land, two if by sea, e.g.
• Something cracked
• Programmer's creation
• It's broken after some thought
• Spy-school subject
• UPC part
• Cracker's target
• It may be cracked by a spy
• Programmer's concern
• It can't be understood until it's broken
• "The Da Vinci ___"
• Bit of flirting
• Bed intruders?
• [I'm kidding!]
• See 85A