Method and a system for embedding textual forensic information

Abstract

A method for automatically embedding information in a digital text, said method comprising: identifying a plurality of positions, in said digital text, that are suitable for introducing modifications into said digital text; identifying modifications suitable for introduction into at least some of said suitable positions in said digital text; selecting at least some of said identified modifications for introduction into said digital text, said selection of said modifications being operable to represent said information; and performing said selected modifications on said digital text, thereby to embed said information.

We claim:  
     
         1 . A method for automatically embedding information in a digital text, said method comprising: 
 identifying a plurality of positions, in said digital text, that are suitable for introducing modifications into said digital text;    identifying modifications suitable for introduction into at least some of said suitable positions in said digital text;    selecting at least some of said identified modifications for introduction into said digital text, said selection of said modifications being operable to represent said information; and    performing said selected modifications on said digital text, thereby to embed said information.    
     
     
         2 . A method according to  claim 1 , wherein said method further comprises the approval of said selection of modifications in said digital text.  
     
     
         3 . A method according to  claim 1 , wherein said modifications include at least one of the following: 
 replacing a character with a substantially similar looking character;    replacing a character with a similarly looking character, wherein said characters only differ in their digital representation;    replacing a character with a similarly looking character, wherein said characters only differ in their Unicode representation;    removing an unprintable character;    adding an unprintable character;    replacing an unprintable character;    exchanging between at least two possible representations of an end of a paragraph; and    exchanging between at least two possible representations of an end of a line.    
     
     
         4 . A method according to  claim 3 , wherein said modifications include at least one of the following: 
 modifying the number of spaces between words;    modifying the number of spaces between paragraphs;    modifying the number of spaces between lines;    modifying the number of spaces at a line ending;    modifying the number of tabs at a line ending;    adding at least one space character at a line ending;    adding at least one tab character at a line ending;    modifying the size of spaces between words;    modifying the size of spaces between paragraphs;    modifying the size of spaces between lines;    modifying the size of spaces between characters;    modifying the number of spaces representing a tab character;    modifying the place of a tab;    replacing a tab character with at least one space;    replacing at least one space with a tab character; and    modifying the size of a tab character.    
     
     
         5 . A method according to  claim 1 , wherein said modifications include at least one of the following: 
 modifying the font of at least one character;    modifying the color of at least one character;    modifying the size of at least one character;    modifying a property of at least one character;    modifying the background of said digital text;    modifying the background of at least one character;    replacing a character with an image similar to said character;    modifying the digital representation of said digital content;    modifying the internal logical division in the digital representation of said digital content;    modifying the classification of a unit in the internal logical division in the digital representation of said digital content;    modifying a property of a unit in the internal logical division in the digital representation of said digital content;    modifying the classification of a paragraph; and    modifying a property of a paragraph.    
     
     
         6 . A method according to  claim 1 , wherein said modifications include at least one of the following: 
 punctuation modifications;    spelling modifications;    spelling modifications that exchange between different valid spellings of the same word; and    spelling modifications that exchange between at least one valid spelling of the a word and at least one invalid spelling of said word.    
     
     
         7 . A method according to  claim 1 , wherein said modifications include at least one of the following: 
 exchanging between some of the following versions of a word built from at least two words: a concatenated version, a version that uses a hyphen for separation and a version separated by a space;    spelling modifications that exchange between an acronym and full verbatim versions of said acronym;    spelling modifications that exchange between at least one shortened version of a word and the full version of said word;    exchanging between a correct version of a word and at least one other word, said other words have similar pronunciation to said correct word;    exchanges between synonyms;    modifications that effect an order of elements within said digital text;    modifications that effect an order of words;    modifications that effect an order of sentences; and    modifications that effect an order of paragraphs.    
     
     
         8 . A method according to  claim 1 , wherein said modifications include at least one of the following: 
 modifications that effect capitalization;    removing at least one word;    adding at least one word;    replacing at least one word;    modifications to diagrams embedded in said digital text;    addition of diagrams embedded in said digital text;    removal of diagrams embedded in said digital text;    modifications to the shadow of at least one character;    exchanging between at least two different grammatical structures; and    modifying the phrasing of at least a part of said digital text such that the changed version remains similar to the original version.    
     
     
         9 . A method according to  claim 1 , wherein said identification of modifications is performed in a manner which takes into consideration limitations imposed by the digital representation of said digital text.  
     
     
         10 . A method according to  claim 1 , wherein said embedded information contains information suitable to identify at least one entry in a database, said database entry containing additional information.  
     
     
         11 . A method according to  claim 1 , wherein said embedded information contains information operable to identify at least one recipient of said digital text.  
     
     
         12 . A method according to  claim 11 , comprising the step of selecting different combinations of said modifications to form different copies of said digital text such that a plurality of recipients of said digital text each receive a personally modified version of said digital text, said different combinations within said embedded information being operable to uniquely identify a respective recipient of each copy.  
     
     
         13 . A method according to  claim 1 , wherein said embedded information contains information operable to identify at least one editor of said digital text.  
     
     
         14 . A method according to  claim 1 , comprising automatically performing said step of identifying positions in said digital text.  
     
     
         15 . A method according to  claim 1 , wherein said step of identifying positions in said digital text, is performed manually.  
     
     
         16 . A method according to  claim 1 , wherein said step of identifying positions in said digital text, is performed such that said positions are distributed in a predefined manner within said digital text.  
     
     
         17 . A method according to  claim 16 , wherein said predefined manner of distribution of said positions within said digital text is a distribution wherein all portions of said digital text larger than a given size contain enough embedded information to reconstruct a predetermined subset of said embedded information.  
     
     
         18 . A method according to  claim 16 , wherein said desirable manner of distribution of said positions within said digital text is a distribution defined such that removal of a significant number of said positions from said digital text results in significant degradation of the value of said digital text.  
     
     
         19 . A method according to  claim 1 , wherein at least part of said embedded information is encoded using at least one of the following: 
 error detection code;    error correction code;    cryptographic signature; and    cryptographic encryption.    
     
     
         20 . A method according to  claim 1 , wherein said identification of suitable modifications is performed in a manner which takes into account the limitations imposed by requirements concerning the quality of said digital text and on the resemblance of said modified text to the original version of said digital text.  
     
     
         21 . A method according to  claim 1 , wherein said selection of said identified modifications is performed so that at least two potential modifications are grouped together, and wherein several versions of said digital text are produced with different embedded information, said group of changes being performed in unison, such that if a modification which is part of said group is performed on one version of said text, all other modifications in said group are also performed on said version.  
     
     
         22 . A method according to  claim 21 , wherein said modifications in said group are in proximity to each other within said digital text.  
     
     
         23 . A method according to  claim 1 , wherein said selection of modifications is performed such as to take into account the amount of information which is to be embedded in said digital text.  
     
     
         24 . A method according to  claim 23 , wherein said amount of information which is to be embedded in said digital text is dictated by at least one of the following considerations: 
 the amount of actual information which needs to be represented by said information embedded in said digital text;    the usage of error correction code;    the usage of error detection code;    the requirements on robustness;    the required number of different versions of said digital text;    the need to embed a database index; and    the need to embed versioning information.    
     
     
         25 . A method according to  claim 1 , wherein said embedded information contains at least one of the following: 
 versioning information;    editing history information;    forensics information;    transfer history information; and    information operable to identify and categorize said digital text.    
     
     
         26 . A method according to  claim 3 , wherein said embedded information is substantially imperceptible.  
     
     
         27 . A method for monitoring digital text by utilizing information embedded in digital texts, said method comprising: 
 embedding information in digital texts it is desired to monitor;    detecting an attempt to use a specific digital text;    determining whether said specific digital text contains said embedded information;    determining whether said specific digital text is one of said digital texts it is desired to monitor according to said embedded information; and    reading said information embedded in said specific digital text.    
     
     
         28 . A method according to  claim 27 , wherein said embedded information is operable to identify the source of said digital text when said digital text is found in at least one of the following states: 
 in the possession of an unauthorized party;    in an unauthorized location;    in an unsecured location; and    in an unsecured format.    
     
     
         29 . A method according to  claim 28 , wherein said embedded information is further operable to identify at least part of the path in which said digital text reached said state.  
     
     
         30 . A method according to  claim 27 , wherein said method further comprises controlling the usage of said digital text according to said embedded information.  
     
     
         31 . A method according to  claim 30 , wherein said embedded information contains at least one limitation about the usage of said digital text.  
     
     
         32 . A method according to  claim 31 , wherein said limitations comprising at least one of the following: 
 limitations about the time in which it is allowable to use said digital text;    limitations about where it is allowable to use said digital text;    limitations about how it is allowable to use said digital text; and    limitations about who is allowed to use said digital text.    
     
     
         33 . A method according to  claim 32 , wherein said controlling is dependent on at least one of the following: 
 the identity of the user performing said usage;    the usage rights of the user performing said usage;    the identity of said digital text;    the risks associated with said usage;    the security mechanisms used in said usage; and    the type of usage.    
     
     
         34 . A method according to  claim 32 , wherein said limitations on how said text is used comprise limitations to at least one of the following: 
 viewing said digital text;    editing said digital text;    transferring said digital text; and    storing said digital text.    
     
     
         35 . A system for controlling usage of a digital text by utilizing information embedded in digital text[?s], said system comprising: 
 at least one computerized information embedding unit operable to embed said information in said digital texts;    at least one computerized information reading unit operable to read said information embedded in said digital texts;    at least one computerized digital text usage unit operable to use said digital texts; and    at least one computerized control unit operable to:    receive notification from said computerized digital text usage unit, said notification indicating said digital text;    receive information from said computerized information reading unit, said information dependent on said information embedded in said digital text and read by said computerized information reading unit; and    instruct said computerized digital text usage unit on a usage policy for said digital text, said usage policy dependent on said information received from said computerized information reading unit.    
     
     
         36 . A system according to  claim 35 , wherein said embedded information is operable to identify the source of said digital text when said digital text is found in the possession of an unauthorized party.  
     
     
         37 . A system according to  claim 35 , wherein said system further comprises at least one database containing at least one entry containing additional information, and wherein said embedded information is operable to be correlated to said entry.  
     
     
         38 . A system according to  claim 35 , wherein said system further comprises at least one computerized document management unit operable to maintain information about digital texts.  
     
     
         39 . A system according to  claim 38 , wherein said computerized document management unit is operable to maintain at least one of the following types of information: 
 versioning information;    editing history information;    usage policy information;    transfer history information; and    category information.    
     
     
         40 . A system according to  claim 38 , wherein said computerized document management system is operable to interact with said computerized control unit.  
     
     
         41 . A system according to  claim 40 , wherein said interaction comprises at least one of the following: 
 said computerized control unit informing said computerized document management unit about usage of said digital text; and    said computerized document management unit sending information to said computerized control unit, said information sent operable to be used by said computerized control unit to create said usage policy.    
     
     
         42 . A system according to  claim 35 , wherein said usage policy comprises at least one of the following: 
 preventing said usage;    restricting said usage;    monitoring said usage;    reporting said usage; and    allowing said usage.    
     
     
         43 . A system according to  claim 35 , wherein said usage policy depends on at least one of the following: 
 the identity of the user performing said usage;    the usage rights of the user performing said usage;    the identity of said digital text;    the identity of the editors of the version of said digital text used in said usage;    the risks associated with said usage;    the security mechanisms used in said usage; and    the type of usage.    
     
     
         44 . A system according to  claim 35 , wherein said usage comprises at least one of the following: 
 viewing said digital text;    editing said digital text;    transferring said digital text; and    storing said digital text.    
     
     
         45 . A system according to  claim 35 , wherein said embedded information contains first indication information, said first indication information indicating at least one element in a group, and wherein said embedded information further contains second indication information, said second indication information indicating said group.  
     
     
         46 . A system according to  claim 35 , wherein said embedded information contains a plurality of information elements, and wherein a subset of said information elements are embedded into said digital text such that said subset of said information elements is encoded in a manner more resilient to a change in said digital text than the embedding of another subset of said information elements.  
     
     
         47 . A system according to  claim 35 , wherein said system further comprises a computerized transformer unit operable to receive a version of a digital text, said version contains both editing changes and embedded information, and wherein said computerized transformer unit is further operable to produce a version of said digital text which contains both said editing changes and different embedded information.