Patent ID: 7117367

Claim:
A method of authenticating a text document with links to a plurality of files by modifying at least a selected attribute of invisible characters on a plurality of inter-word intervals of the text document, comprising: a) computing a one-way hash function of each file of the plurality of files to obtain a hash value composed of a subset of hash digits for each file, b) encoding each subset of a plurality of subsets of space characters in the text document by replacing in each subset of space characters, the value of the selected attribute for each space character by a corresponding encoded hash digit of each subset of hash digits corresponding to each one of the plurality of files, c) computing an electronic signature of the encoded text document by using a public-key algorithm composed of a subset of signature digits, and d) encoding another subset of space characters in the encoded text document by replacing the value of the selected attribute for each space character by a corresponding encoded signature digit.