'Returns True if a validated nonce is stale. The nonce contains a
timestamp in plaintext and also a secure hash of the timestamp. You should
first validate the nonce to ensure the plaintext timestamp is not spoofed.'

def is_nonce_stale(self, max_age_seconds=600):

    try:
        (timestamp, hashpart) = self.nonce.split(':', 1)
        if ((int(timestamp) + max_age_seconds) > int(time.time())):
            return False
    except ValueError:
        pass
    if self.debug:
        TRACE('nonce    is    stale')
    return True
