1. A method of encoding hidden auxiliary data in a text document comprising: using an electronic processor for: forming a message; spreading the message over a carrier signal to yield a spread spectrum message; modifying distances of existing spaces between words to encode a machine-detectable interword modification in the document based on elements of the spread spectrum message, wherein interword modifications are controlled to form a machine-detectable message in the text document.
10. A non-transitory computer readable medium on which is stored instructions to cause an electronic processor to perform the method of claim 1 .