Data integrity verification is utmost important in trusted computing and Merkle trees are usually employed in implementation. However, the efficiency of data authentication is regarded as the main bottleneck in performance. In this paper, we propose an efficient data authentication protocol appropriate for a USB flash disk, named UTrustDisk (a trust-based intelligent disk). In our scheme, verification is speed up by using WH universal hash function and speculative caching. WH algorithm can hash message into a short digest at a high speed and the collision probability is almost negligible. Speculative caching will cache the potential hot chunks which can reduce the memory bandwidth pollution. In our experiments the success rate of speculation reaches 94.5% because the UTrustDisk's access mode is usually sequentially. The comparative experiment results show that SWHash average write throughput is 44.8% higher than NH scheme and 316% higher than SHA-1 scheme.