For relatively small data sets in CSV format, you can use the in-browser utility-- which is quite convenient (no installation, no security concerns) at https://zsvhub.com/playground/. A subset of the features there are available in a native command-line utility (all open-source-- see https://github.com/liquidaty/zsv), to which the "obfuscate" feature that is currently available in the playground will soon be available and is anticipated to be extremely fast (in keeping with the project's current status as the fastest CSV parser). Full disclosure: I am one of the contributors / authors of zsv/lib and zsvhub