UC Secure Private Branching Program and Decision Tree Evaluation

Branching program (BP) is a DAG-based non-uniform computational model for L/poly class. It has been widely used in formal verification, logic synthesis, and data analysis. As a special BP, a decision tree is a popular machine learning classifier for its effectiveness and simplicity. In this work, we propose a UC-secure efficient 3-party computation platform for outsourced branching program and/or decision tree evaluation. We construct a constant-round protocol and a linear-round protocol. In particular, the overall (online + offline) communication cost of our linear-round protocol is O(d(\ell + \log m+\log n)) O(d(ℓ+logm+logn)) and its round complexity is 2d-1 2d-1 , where m m is the DAG size, n n is the number of features, \ell ℓ is the feature length, and d d is the longest path length. To enable efficient oblivious hopping among the DAG nodes, we propose a lightweight 1-out-of-N N shared OT protocol with logarithmic communication in both online and offline phase. This partial result may be of independent interest to