The issuer of the token is not a trusted issuer

Hi, I have a problem in authorization saml token to sharepoint.

I've got error like below:

[FaultException`1: The issuer of the token is not a trusted issuer.]
   Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.ReadResponse(Message response) +222
   Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst, RequestSecurityTokenResponse& rstr) +83
   Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst) +37

It looks like there is a problem with certificate but I don't know how to resolve this ;/

Please tell me if I should use certificate in Sharepoint as SPTrustedTokenIdentityTokenIssuer which IDP STS uses for signning saml assertion token? or SPTrustedTokenIdentityTokenIssuer should be another certificate?

Thanx for any help.