Patent ID: 7913313

Claim:
A method of embedding into a text document generated by a licensed software a License Identification Signature of the software, the method comprising: converting all space characters of the text document to identical black space characters comprising a black color; after said converting, computing a Document Hash Value (DHV) comprising a one-way hash of the text document, wherein each original copy of the software has been assigned a unique Software License Code (SLC) and a unique License Identification Key (LIK) by a Licensing Authority; computing a License Identification Code (LIC) comprising a cryptographic digest of the DHV by applying a cryptographic hash function to the DHV and using the LIK as a key; forming a License Identification Signature (LIS) comprising the SLC, the DHV, and the LIC; forming an encoded LIS by mapping the digits of the LIS to corresponding character attributes, said encoded LIS comprising the corresponding character attributes respectively corresponding to the digits of the LIS; and embedding the corresponding character attributes into respective consecutive black space characters starting with the first black space character at the beginning of the text document.