anchor.diff:        var artifact = await  mgrs.findArtifact(idArtifact);
         var currentuser = userService.currentAuthenticatedUser();
   
  -      var downloadInfo = await downloadInfo(artifact,currentuser);
  +      var downloadInfo = await ArtifactService.downloadInfo(artifact,currentuser);
   
         return new Response(200, downloadInfo.toJson());
       } catch(error,stack){
  
positive.code:       var tokenArtifactId = tokenInfo["id"];
        //artifactID same as those in token
        if (idArtifact != tokenArtifactId){
          return new RpcError(401,"ARTIFACT_ERROR","Access denied");
        }
  
        var artifact = await mgrs.findArtifact(idArtifact);
  
negative.code:     now = now.add(new Duration(minutes: tokenValidity));
  
      final token = {
        'id':artifact.uuid,
        'expireAt': now.millisecondsSinceEpoch,
        'user': currentuser!=null ? currentuser.email : "no user"
      };
  