Syntactic tools for text watermarking

Abstract

This paper explores the morphosyntactic tools for text watermarking and develops a syntax-based natural language watermarking scheme. Turkish, an agglutinative language, provides a good ground for the syntax-based natural language watermarking with its relatively free word order possibilities and rich repertoire of morphosyntactic structures. The unmarked text is first transformed into a syntactic tree diagram in which the syntactic hierarchies and the functional dependencies are coded. The watermarking software then operates on the sentences in syntax tree format and executes binary changes under control of Wordnet to avoid semantic drops. The key-controlled randomization of morphosyntactic tool order and the insertion of void watermark provide a certain level of security. The embedding capacity is calculated statistically, and the imperceptibility is measured using edit hit counts.