A scheme based on RSA and threshold secret sharing is proposed

and it can manage reputation information in P2P networks.This scheme uses theory of threshold secret sharing to protect reputation information

and information will be divided into n secret shadows and distributed to different participants

who act as rightful ones.Reputation information which was divided can be reconstructed by any of t or more participants

but any fewer participants cant do this according to the theory.In order to protect reputation information

a validation shadow will also be sent with secret shadow to the participant.Any participant will be recognized at once if he is unlawful participant or offers false secret shadow

unless he can break through RSA cryptography

so this scheme can be proved secure enough.