Method of protecting paper and electronic text documents through a hidden biometric identifier based on a signature

The paper aims at studying some methods of coding information in text containers. It proposes a method of embedding a digital watermark to the text that is based on biometrical characteristics of the document's author. The information capacity is defined, it is 0.02 in respect of a bit/symbol proportion. A method of checking electronic and paper documents for their authenticity and unauthorized changes is developed.