METHOD FOR PROTECTING DATA

• US 20150324590A1
• Filed: 03/26/2012
• Published: 11/12/2015
• Est. Priority Date: 03/26/2012
• Status: Active Grant

• Current Assignee: Irdeto B.V. (MultiChoice Group Ltd.)
• Original Assignee: Irdeto Canada Corporation (MultiChoice Group Ltd.)
• Inventors: KRTEN, Robert, DONG, Hongrul, LIEM, Clifford
• Granted Patent: US 9,454,666 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/137 Hash-based content-based indexing of textual data G06F16/31
• CPC Class Codes: G06F 21/125 by manipulating the program code, e.g. source code, compiled code, interpreted code, machine code
• CPC Class Codes: G06F 21/14 against software analysis or reverse engineering, e.g. by obfuscation
• CPC Class Codes: G06F 21/60 Protecting data
• CPC Class Codes: G06F 21/64 Protecting data integrity, e.g. using checksums, certificates or signatures
• CPC Class Codes: G06F 2221/2107 File encryption
• CPC Class Codes: H04L 2209/16 Obfuscation or hiding, e.g. involving white box
• CPC Class Codes: H04L 9/0894 Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage
• CPC Class Codes: H04L 9/3239 involving non-keyed hash functions, e.g. modification detection codes [MDCs], MD5, SHA or RIPEMD

Abstract

In the present disclosure, a hash function is computed over a known image, for example, an address range in a program. The result of the hash function is known to be the same at two distinct points in time, before the program is run, i.e. signing at build-time, and during the running of the program, i.e. run time. The value that the programmer wishes to hide, i.e. the secret value, is also known at build-time. At build-time, the secret value is combined with the hash in such a way that the combining operation can be reversed at run time. This combined value, i.e. the salt, is stored along with the program. Later, at runtime, the program computes the same hash value as was computed at signing time, and does the reverse combining operation in order to reveal the secret value.

Claims

1. A method of protecting sensitive data comprising the steps of:

during build time, hashing an image to produce a first hash;

combining sensitive data with the first hash to form a salt; and

storing the salt;

at runtime, hashing the image to produce a second hash;

retrieving the salt;

combining the second hash and the salt to recover the sensitive data;

combining a first value with the image; and

comprising the step of splitting the sensitive data into at least two portions, combining a first value with the image, combining a first portion of the sensitive data with the first hash to form a first salt and combining a second value with the image, combining a second portion of the sensitive data with the first hash to form a second salt.

2. The method of claim 1, wherein the step of retrieving the salt retrieves first and second salts and the step of combining the second hash, combines the second hash with the first and second salts to recover first and second portions, respectively, of the sensitive data.

3. The method of claim 2, further comprising the step of hashing the first and second hashes to produce third and fourth hashes and comparing the third and fourth hashes to determine if they are the same and verifying the sensitive data if they are the same.

4. The method of claim 3, wherein the step of combining sensitive data and the third hash value includes combining the sensitive data with random data.

5. The method of claim 4, wherein the step of combining sensitive data and the third hash value includes combining the sensitive data with random data and combining the output with the random data and the third hash value.

6. The method of claim 5, wherein the sensitive data is an instruction address.

7. The method of claim 6, wherein the instruction address includes at least one of a branching address and callback function address.

8. The method of claim 6 or 7, wherein the instruction address has one of 32 bits and 64 bits.

9. The method of claim 1, wherein the image is a portion of any file.

10. The method of claim 9, wherein the image is a portion of an executable file.

11. A method of protecting sensitive data comprising the steps of:

during build time, hashing an image to produce a first hash;

hashing the first hash to produce a second hash;

combining sensitive data with the second hash to produce a combined value;

combining the first hash and the combined value to form a salt; and

storing the salt;

at runtime, hashing the image to produce a third hash;

hashing the third hash to produce a fourth hash;

retrieving the salt;

combining the third hash and the salt to recover the combined value;

comparing the second hash from the recovered combined value with the fourth hash and if they are the same;

recovering the sensitive data from the remainder of the combined data.

12. The method of claim 11, wherein the step of combining sensitive data and the second hash value includes the step of adding random data.

13. A method of claim 12 wherein the step of combining sensitive data and the second hash value includes exclusive oring the sensitive data with the random data.

14. The method of claim 13, wherein the step of combining sensitive data and the second hash value includes exclusive oring the sensitive data with the random data and combining the output with the random data and the second has value.

15. The method of claim 14, wherein the sensitive data is an instruction address.

16. The method of claim 15, wherein the instruction address includes at least one of a branching address and callback function address.

17. The method of claim 15 or 16, wherein the sensitive data is an instruction address has one of 32 bits and 64 bits.

18. The method of claim 11, wherein the image is a portion of any file

19. The method of claim 18, wherein the image is a portion of an executable file

20. The method of claim 19 wherein the image has a value combined therewith

21. The method of claim 20 wherein the value corresponds to an instruction address

22. The method of claim 21 wherein there are a plurality of instruction addresses, each address having a corresponding value combined with the image.

23. The method of claim 22 wherein the step of combining the first hash and the combined value to form a salt does so for each corresponding value combined with the image to produce a corresponding plurality of salts.

24. (canceled)

25. (canceled)