Related Clues:

• 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 ___"
• Bed intruders?
• Do programming work
• Zip --
• Write software
• Software basis
• Bar closing?
• Encryption or set of rules
• Cryptogram or set of standards
• Computer instructions