Trust,　the　most　fundamental　concept　in　Trusted　Computing,　is　a　pervasive　notion　and,　as　such,　has　been　studied　thoroughly　in　a　variety　of　different　fields.　Based　on　a　survey　of　trust　and　security,　two　formal　definitions　for　trust　in　Trusted　Computing　are　presented　in　this　paper:　one　for　trust　between　coequal　components　(the　direct　trust)　and　the　other　for　trust　in　specialization-employed　environment　(the　recommended　trust).　Therefore,　the　rationality　of　the　properties　of　trust　relation　has　been　comprehensively　discussed　in　detail,　such　as　reflexive,　symmetric,　and　conditionally　transitive.　Finally,　several　prospective　insights　are　proposed　towards　modeling　a　trusted　system　on　basis　of　those　definitions.　©　2010　IEEE.