This document proposes a secure and efficient multi-keyword ranked search scheme over encrypted cloud data. It utilizes a tree-based index structure and "Greedy Depth-first Search" algorithm to enable sub-linear search times. The scheme supports dynamic insertion and deletion of documents without privacy leakage. It uses a secure k-Nearest Neighbor algorithm to encrypt index and query vectors, allowing accurate relevance scoring between encrypted vectors. The scheme aims to provide secure, efficient, and accurate multi-keyword ranked search and dynamic updates over outsourced encrypted data in the cloud.