Method of invisibly embedding into a text document the license identification of the generating licensed software

• US 20050262034A1
• Filed: 06/04/2002
• Published: 11/24/2005
• Est. Priority Date: 06/12/2001
• Status: Active Grant

• Current Assignee: Kyndryl Incorporated
• Original Assignee: International Business Machines Corporation
• Inventors: Carro, Fernando Incertis
• Granted Patent: US 7,475,429 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 21/10 Protecting distributed programs or content, e.g. vending or licensing of copyrighted material protection in video systems or pay television H04N7/16 ; Digital rights management [DRM]
• CPC Class Codes: G06F 21/6209 to a single file or object, e.g. in a secure envelope, encrypted and accessed using a key, or with access control rules appended to the object itself

Abstract

Method of invisibly embedding into a text document generated by a licensed software the License Identification Signature of the software 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, such a method comprising the steps of computing a Document Hash Value (DHV) of the text document (12), getting from the DHV a License Identification Code (LIC) of the text document by using the LUK (14), and embedding (18) invisibly into the text document the License Identification Signature (LIS) formed by the SLC, DHV and LIC after the LIS has been encoded by using character attributes.

Claims

1. A method of embedding into a text document generated by a licensed software License Identification Signature of the software 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,

the method comprising:

computing a Document Hash Value (DHV) of the text document,

obtaining from the DHV a License Identification Code (LIC) of the text document by using the LIK, and

embedding invisibly into the text document the License Identification Signature (LIS) formed by the SLC, DHV and LIC after the LIS has been encoded by using character attributes.

2. The method according to claim 1, wherein the text document is transformed into canonical form by setting on at least a part of the inter-word intervals of the document, values of at least a selected attribute to a same default value.

3. The method according to claim 2, wherein computing a DHV is performed by applying on the text document transformed into canonical form using a one-way hash function.

4. The method according to claim 2, wherein obtaining an LIC is performed by computing a cryptographic digest of the DHV of utilizing a cryptographic hash function.

5. The method according to claim 2, wherein embedding comprises:

selecting at least one attribute that is invisible on space characters used as inter-word intervals,

encoding the LIS to be embedded into the text document as an ordered set of values corresponding to different values of the selected attribute,

selecting a set of inter-word intervals among the inter-word intervals in the text document in canonical form corresponding to a set of space characters to be used for embedding the LIS into the text document, and

replacing on each space character of the set of space characters, default attribute values by the corresponding encoded LIS.

6. The method according to claim 5, wherein the LIS to be embedded is encoded by using a set of attribute values, the set of attribute values being encoded by establishing a correspondence table between the attribute values and digits representing data to be embedded.

7. The method according to claim 6, wherein the LIS to be embedded is a sequence of figures which can be each one of figures 0, 1, 2, . . . , N-1 in the N base, the figures corresponding respectively to N selected attribute values.

8. The method according to claim 7, wherein the selected attribute is character color, the attribute values corresponding to N different colors which can be selected for the color attribute.

9. The method according to claim 8, wherein the LIS to be embedded is represented by decimal figures in the 10 base (N=10), each figure 0 to 9 being associated respectively to a color defined by the character color attribute.

10. The method according to claim 7, wherein two attributes are used in combination so that each of the figures 0, 1, 2, . . . N-1 in the N base corresponds respectively to a combination of a selected value of a first attribute and a selected value of a second attribute.

11. The method according to claim 10, wherein second attribute is italic format of a character, the attribute value corresponding to italic or non italic.

12. A method of checking a text document received by a receiving communication system wherein the text document includes a hidden License Identification Signature (LIS) associated with document generating software used for generating the text document and which has been embedded in the document by modifying selected invisible attributes on space characters, comprising:

extracting the LIS from the selected invisible attributes on the space characters of the received text document, and

sending the extracted LIS to a Licensing Authority which has a Master License Database at its disposal for retrieving a License Identification Key (LIK) associated with the document generating software in response to a Software License Code (SLC) included in the LIS.

13. The method according to claim 12, wherein a License Identification Code (LIC) is computed from a Document Hash Value (DHV) included in the LIS by using the LIK as a key and a same function that was applied for generating the LIS, the LIC being compared with the received LIC included in the LIS in order to authenticate the received text document.

14. (canceled)

15. (canceled)

16. A system for embedding into a text document generated by a licensed software a License Identification Signature of the software 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, comprising:

means for computing a Document Hash Value (DHV) of the text document;

means for obtaining from the DHV a License Identification Code (LIC) of the text document by using the LIK; and

means for embedding invisibly into the text document the License Identification Signature (LIS) formed by the SLC, DHV and LIC after the LIS has been encoded by using character attributes.

17. A system for checking a text document received by a receiving communication system wherein the text document includes a hidden License Identification Signature (LIS) associated with document generating software used to generate the text document and which has been embedded in the document by modifying selected invisible attributes on the space characters, comprising:

extracting the LIS from the selected invisible attributes on the space characters of the received text document, and

sending the extracted LIS to a Licensing Authority which has a Master License Database at its disposal for retrieving a License Identification Key (LIK) associated with document generating software in response to a Software License Code (SLC) included in the LIS.

18. A computer program product for embedding into a text document generated by a licensed software a License Identification Signature of the software 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, comprising:

a computer readable medium having computer readable program code embodied therein, the computer readable program code comprising;

computer readable program code configured to compute a Document Hash Value (DHV) of the text document;

computer readable program code configured to obtain from the DHV a License Identification Code (LIC) of the text document by using the LIK; and

computer readable program code configured to embed invisibly into the text document the License Identification Signature (LIS) formed by the SLC, DHV and LIC after the LIS has been encoded by using character attributes.

19. A computer program product for checking a text document received by a receiving communication system wherein the text document includes a hidden License Identification Signature (LIS) associated with document generating software used to generate the text document and which has been embedded in the document by modifying selected invisible attributes on the space characters, comprising:

a computer readable medium having computer readable program code embodied therein, the computer readable program code comprising;

computer readable program code configured to extract the LIS from the selected invisible attributes on the space characters of the received text document, and

computer readable program code configured to send the extracted LIS to a Licensing Authority which has a Master License Database at its disposal for retrieving a License Identification Key (LIK) associated with document generating software in response to a Software License Code (SLC) included in the LIS.