Electronic book security features
A method and system for fingerprinting a content item is described, the content item including a set of content item elements E, providing information uniquely associated with a single user including a string of bits S 0 , parsing S 0 into a plurality of substrings which are functions of S 0 , providing a matrix of content item replacement elements, each row of which includes, for each member of E, an array of content item replacement elements for E i , uniquely associating each substring of S 0 so that for every substring there exists a corresponding element of E, for every substring, replacing at least one instance of the corresponding element E in the content item with one substitute matrix element for the corresponding substring, and outputting a replacement content item including the result of the replacing, the substitute matrix elements being chosen according to at least one similarity criterion.
1. A method for fingerprinting a content item, the method comprising:
providing the content item, the content item comprising a set of content item elements, the set of content item elements denoted E, such that E={E 1 , E 2 , . . . E i , . . . E m };
providing information uniquely associated with a single user, the information comprising a string of bits, hereinafter denoted S 0 ;
parsing S 0 into a plurality of subsequences of strings of bits, hereinafter denoted S 1 , . . . , S n , the parsing being performed such that S 0 equals a function of S 1 , . . . , S n ;
providing a matrix of content item replacement elements, the matrix denoted R, each row of matrix R comprising, for at least each one of n members of set E, an array of content item replacement elements for E i denoted R i , such that R i ={R i1 , . . . R ij };
uniquely associating, by a processor, each one of the possible combinations of subsequences for each of S 1 , . . . , S n with one matrix element of matrix R, so that for every one of the possible combination of subsequences of bits and for each S 1 , . . . , S n there exists a corresponding element of E;
for every one of S 1 , . . . , S n replacing at least one instance of the corresponding element E in the content item with the associated one matrix element of matrix R for the corresponding one of S 1 , . . . , S n ; and
outputting a replacement content item comprising the result of the replacing,
wherein the members of R i for each E i are chosen according to at least one criterion of similarity to the content item E i to be replaced.
2. The method of claim 1 and also comprising storing a record indicating which matrix element of matrix R replaces which subsequence of S 1 , . . . , S n .
3. The method according to claim 1 and wherein the choosing according to a similarity criterion comprises choosing from a table.
4. The method according to claim 3 and wherein the table comprises a plurality of Unicode characters.
5. The method according to claim 3 and wherein the table comprises a plurality of colors.
6. The method according to claim 3 and wherein the table comprises a plurality of gray scale levels.
7. The method according to claim 1 and wherein the content item comprises a text based content item.
8. The method according to claim 7 and wherein the E i comprised in the text based content item comprises a Unicode character.
9. The method according to claim 7 and wherein the E i comprised in the text based content item comprises at least one pixel displayed in one character.
10. The method according to claim 1 wherein the content item comprises a graphic content item.
11. The method according to claim 10 and wherein the E i comprised in the graphic content item comprises at least one pixel.
12. The method according to claim 1 and wherein the content item comprises a sound based content item.
13. The method according to claim 1 and wherein the content item comprises a video based content item.
14. The method according to claim 13 and wherein the E i comprised in the video based content item comprises at least one pixel.
15. A system for fingerprinting a content item, the system comprising:
a content item comprising a set of content item elements, the set of content item elements denoted E, such that E={E 1 , E 2 , . . . E i , . . . E m };
information uniquely associated with a single user, the information comprising a string of bits, hereinafter denoted S 0 ;
a parser operative to parse S 0 into a plurality of subsequences of strings of bits, hereinafter denoted S 1 , . . . , S n , the parsing being performed such that S 0 equals a function of S 1 , . . . , S n ;
a matrix of content item replacement elements, the matrix denoted R, each row of matrix R comprising, for at least each one of n members of set E, an array of content item replacement elements for E i denoted R i , such that R i ={R i1 , . . . R ij };
a processor which uniquely associates each one of the possible combinations of subsequences for each of S 1 , . . . , S n with one matrix element of matrix R, so that for every one of the possible combination of subsequences of bits and for each S 1 , . . . , S n there exists a corresponding element of E;
a replacer, operative to replace, for every one of S 1 , . . . , S n , at least one instance of the corresponding element E in the content item with the associated one matrix element of matrix R for corresponding one of S 1 , . . . , S n ; and
a replacement content item outputting unit which outputs a replacement content item comprising the result of the replacing,
wherein the members of R i for each E i are chosen according to at least one criterion of similarity to the content item E i to be replaced.
16. A system for fingerprinting a content item, the system comprising:
means for providing the content item, the content item comprising a set of content item elements, the set of content item elements denoted E, such that E={E 1 , E 2 , . . . E i , . . . E m };
means for providing information uniquely associated with a single user, the information comprising a string of bits, hereinafter denoted S 0 ;
means for parsing S 0 into a plurality of subsequences of strings of bits, hereinafter denoted S 1 , . . . , S n , the parsing being performed such that S 0 equals a function of S 1 , . . . , S n ;
means for providing a matrix of content item replacement elements, the matrix denoted R, each row of matrix R comprising, for at least each one of n members of set E, an array of content item replacement elements for E i denoted R i , such that R i ={R i1 , . . . R ij };
means for uniquely associating each one of the possible combinations of subsequences for each of S 1 , . . . , S n with one matrix element of matrix R, so that for every one of the possible combination of subsequences of bits and for each S 1 , . . . , S n there exists a corresponding element of E;
for every one of S 1 , . . . , S n means for replacing at least one instance of the corresponding element E in the content item with the associated one matrix element of matrix R for the corresponding one of S 1 , . . . , S n ; and
means for outputting a replacement content item comprising the result of the replacing,
wherein the members of R i for each E i are chosen according to at least one criterion of similarity to the content item E i to be replaced.