We address the issue of asserting the accuracy of Internet coordinates advertised by nodes of Internet coordinate systems during distance estimations. Indeed, some nodes may even lie deliberately about their coordinates to mount various attacks against applications and overlays. Our proposed method consists in two steps: 1) establish the correctness of a node's claimed coordinate by using the Surveyor infrastructure and malicious embedding neighbor detection proposed in our previous work on securing the coordinates embedding phase; and 2) issue a time limited validity certificate for each verified coordinate. Validity periods are computed based on an analysis of coordinate inter-shift times observed by Surveyors. By doing this, each surveyor can estimate the time until the next shift and thus, can limit the validity of the certificate it issues to regular nodes for their calculated coordinates. Our method is illustrated on a trace collected from a Vivaldi system deployed on PlanetLab, where inter-shift times are shown to follow long-tail distribution (lognormal distribution in most cases, or Weibull distribution otherwise). We validate the effectiveness of our method by measuring the impact of a variety of attacks on distance estimates.