A trust inference framework

including a delegation-based trust model and a subjective-based trust model and its policy’s formal description

is introduced.After giving a unified formal definition for the trust models

trust propagation principles including concatenation rule and aggregation rule based on Dempster-Shafer theory

are proposed.The model can process the uncertainty evidences besides the states of affirmative and negative ones.According to the simulation results

the probability of uncertainty decreases when the recommended aggregating nodes are to be joined in

which can be used to restrain Sybil attacks and Whitewashing attacks behavior in decentralized environments.