1. A system comprising: one or more processing elements; an object detection module communicatively coupled to or integrated with the one or more processing elements and configured to detect a first object when the first object is in view of a first video camera associated with a first site; a feature vector module communicatively coupled to or integrated with the one or more processing elements and configured to extract a first feature vector from the first object; a preprocessing module communicatively coupled to or integrated with the one or more processing elements and configured to perform local processing of the first feature vector by normalizing the first feature vector and quantizing the first feature vector into an integer value to form a first secure input; a garbled circuit generator communicatively coupled to or integrated with the one or more processing elements and configured to generate a Boolean circuit for a jointly-computed portion of a vector distance function, wherein inputs to the Boolean circuit comprise the first secure input from the first site and a second secure input from a second site, the second secure input generated by processing a second feature vector generated from a second object that was in view of a second video camera associated with the second site; a match query module communicatively coupled to or integrated with the one or more processing elements and configured to send a query to the second site to request participation in solving the jointly-computed portion of the vector distance function; and a joint computation module communicatively coupled to or integrated with the one or more processing elements and configured to solve the jointly-computed portion of the vector distance function with the second site to determine if the first object is the same as the second object.