1. A method for desensitizing character strings, comprising: ordering, by a processing device, a set of sensitive character strings; generating, by the processing device, a tree having a plurality of nodes corresponding to sensitive characters of the sensitive character strings; desensitizing, by the processing device, the sensitive characters on corresponding nodes of the tree in depth-first order, wherein the desensitizing includes assigning desensitization characters from a set of ordered desensitization characters to respective ones of the sensitive characters; and generating, by the processing device, a desensitized character string set having a same ordering as the ordered set of sensitive character strings, the desensitized character string set including desensitized character strings corresponding to respective ones of the sensitive character strings, wherein the desensitized character strings include respective strings of the desensitization characters.