Collaboration　between　IoT　end-devices　and　edge　servers　or　idle　devices　enables　offloading　of　computational　tasks,　providing　an　effective　solution　to　address　inherent　limitations　in　computational　resources,　storage　capacity,　and　energy　efficiency.　However,　IoT　network　openness　introduces　security　challenges,　such　as　privacy　breaches,　data　security,　and　＂free-riding＂　attack.　Securing　computational　offloading　is　crucial　for　service　quality　and　reliability.　In　this　article,　we　introduce　a　comprehensive　approach　to　address　these　challenges.　First,　trust　metrics　are　performed　at　the　level　of　resource　requester　and　resource　provider　respectively,　and　the　trust　level　of　both　parties　is　matched　to　reduce　the　adverse　effects　of　malicious　devices　or　servers　on　computing　offloading.　Then,　a　distributed　decision-making　method　based　on　game　theory　is　designed　to　improve　the　performance　of　the　algorithm　and　avoid　the　single-point-of-failure　problem　through　the　joint　participation　of　multiple　edge　servers　in　decision-making.　Finally,　a　blockchain-based　task　offloading　process　control　strategy　is　used　to　deal　with　the　＂free-riding＂　attack.　The　results　of　simulation　experiments　show　the　effectiveness　of　our　proposed　offloading　decision-making　method.