A potential vulnerability of the contestation design is the lack of active higher-tier provers, especially since contestations are infrequent. To maintain a pool of available high-tier provers, Taiko introduces a mechanism that randomly assigns a minimum required tier for each new block. The likelihood of a block being assigned a higher tier is inversely proportional to the tier level; for instance, only 5% of blocks might require SGX+ZKP, while 20% demand ZKP, leaving the majority to require just SGX. This ensures that ZK provers always have work to keep them engaged and profitable.