Abstract: A computer-implemented method for securely detecting data similarities may include (1) identifying a private data object subject to comparison to determine a similarity with at least one potentially similar data object, (2) establishing a connection between a client system and a server that is not authorized to access the private data object, (3) generating a summary of the private data object by applying a summary generation protocol between the client system and the server to the private data object without exposing plaintext from the private data object to the server and without exposing a parameter of the summary generation protocol to the client system, and (4) computing the similarity between the private data object and the potentially similar data object by using the summary of the private data object and a summary of the potentially similar data object. Various other methods, systems, and computer-readable media are also disclosed.