The Shortest Verification Path of the MHT Scheme for Verifying Distributed Data

Abstract

One of the most common approaches for enhancing network performance is to retrieve data from nearby data holders that have previously obtained the desired data, not only from the original data source itself. In this case, since a data receiver cannot identify a practical data sender, it is necessary to verify both the received data and the data sender. Moreover, a data sender generally fragments the data into several small segments and sends them. Therefore, if these segments are retrieved from multiple unknown senders, the receiver must verify every segment to safely use the data. MHT (Merkle hash tree) is suitable for efficiently verifying the set of segments shared in the network. NDN (named-data networking) and Bitcoin utilize MHT to verify transmitted data. However, a data authentication scheme based on the MHT has an inefficient factor that repeatedly computes the same node values of the MHT and are repeatedly computed. The larger the size of the MHT is, the greater the number of calculation iterations. Therefore, as a result, the authentication scheme’s inefficiency is also more severe. When a sender transmits data consisting of many segments through NDN, the data authentication time may take longer than the data transmission time. Hence, in this paper, the degree of the MHT’s inefficiency and the pattern of the iterated operation of the MHT are analyzed first. The proposed improvement is to find repeatedly used node values, store them internally, and use the stored node values without recalculation when required to reuse them. For that process, a rule to select such node values is given. Additionally, when verifying the leaf node value of the MHT, the MHT-based authentication scheme asks a verifier to compute all node values on the path from the leaf node to the root node of the MHT. This paper demonstrates the proposed shortest path selection for verifying the leaf node value. The proposed scheme, using saved node values and the shortest path, reduces the computational overhead of the MHT and improves service latency. It has been proven from performance evaluations that the proposed scheme decreases the computational overhead by more than one-third if the number of segments is more than 1024.