Verified Query Results from Hybrid Authentication Trees

We address the problem of verifying the accuracy of query results provided by an untrusted third party Publisher on behalf of a trusted data Owner. We propose a flexible database verification structure, the Hybrid Authentication Tree (HAT), based on fast cryptographic hashing and careful use of a more expensive one-way accumulator. This eliminates the dependence on tree height of earlier Merkle tree based proposals and improves on the VB tree, a recent proposal to reduce proof sizes, by eliminating a trust assumption and reliance on signatures. An evaluation of the Hybrid Authentication Tree against the VB tree and Authentic Publication showing that a HAT provides the smallest proofs and faster verification than the VB tree. With moderate bandwidth limitations, the HATs low proof overhead reduces transfer time to significantly outweigh the faster verification time of Authentic Publication. A HAT supports two verification modes that can vary per query and per Client to match Client resources and applications. This flexibility allows the HAT to match the best performance of both hash based and accumulator based methods.