def verifyChain(self, anchors, untrusted=None):
        """
        Perform verification of certificate chains for that certificate.
        A list of anchors is required. The certificates in the optional
        untrusted list may be used as additional elements to the final chain.
        On par with chain instantiation, only one chain constructed with the
        untrusted candidates will be retained. Eventually, dates are checked.
        """
        untrusted = untrusted or []
        for a in anchors:
            chain = Chain(self + untrusted, a)
            if len(chain) == 1:             # anchor only
                continue
            # check that the chain does not exclusively rely on untrusted
            if any(c in chain[1:] for c in self):
                for c in chain:
                    if c.remainingDays() < 0:
                        break
                if c is chain[-1]:      # we got to the end of the chain
                    return chain
        return None