Back when naval communication was radio communication of manually keyed morse code, one major source of naval intelligence was recognizing the "hand" transmitti

Back when naval communication was radio communication of manually keyed morse code, one major source of naval intelligence was recognizing the "hand" transmitting messages via the timing patterns of key entry. The messages were encrypted and that wasn't broken, but the timing patterns were essentially in the clear and gave up some useful information. I wouldn't be surprised if you could generate signatures from the timing patterns of text input events in javascript, too.