Software self-checking systems and methods

• US 8,001,388 B2
• Filed: 07/16/2009
• Issued: 08/16/2011
• Est. Priority Date: 06/13/2001
• Status: Active Grant

• Current Assignee: Intertrust Technologies Corporation (Fidelio Acquisition Co LLC)
• Original Assignee: Intertrust Technologies Corporation (Fidelio Acquisition Co LLC)
• Inventors: Matheson, Lesley R., Sheehan, Casey, Tarjan, Robert E., Home, William G.
• Primary Examiner(s): Song; Hosuk
• Application Number:
  US12/504,567
• Publication Number:
  US 20100017620A1
• Time in Patent Office: 761 Days
• Field of Search: 713/176, 713/181, 713/187, 726/22, 726 26- 27, 714/37
• US Class Current: 713/187
• CPC Class Codes: G06F 11/3624 by performing operations on the source code, e.g. via a compiler
• CPC Class Codes: G06F 21/52 during program execution, e.g. stack integrity ; Preventing unwanted data erasure; Buffer overflow
• CPC Class Codes: G06F 21/54 by adding security routines or objects to programs
• CPC Class Codes: G06F 2221/2143 Clearing memory, e.g. to prevent the data from being stolen
• CPC Class Codes: G06F 2221/2149 Restricted operating environment
• CPC Class Codes: G06F 3/0623 in relation to content
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0673 Single storage device

Abstract

Software self-checking mechanisms are described for improving software tamper resistance and/or reliability. Redundant tests are performed to detect modifications to a program while it is running. Modifications are recorded or reported. Embodiments of the software self-checking mechanisms can be implemented such that they are relatively stealthy and robust, and so that it they are compatible with copy-specific static watermarking and other tamper-resistance techniques.

Claims

1. A method comprising:

(a) inserting a plurality of correctors into object code of a program embodied on a non-transitory computer-readable medium;

(b) assigning self-checking code sequences to overlapping portions of the program, each of said portions containing at least one corrector, wherein each self-checking code sequence is operable to calculate a function of at least one of said portions; and

(c) assigning values to the correctors, the value of each corrector being chosen such that the function calculated by self-checking code sequence assigned to a given portion of the program containing a given corrector results in a predefined value when the given portion has not been improperly modified.

2. The method as in claim 1, in which the self-checking code sequences are distributed in a relatively uniform fashion throughout the program'"'"'s object code.

3. The method as in claim 2, in which the plurality of correctors are inserted between basic blocks of the program'"'"'s object code.

4. The method as in claim 1, further comprising:

inserting watermark values into the program.

5. The method as in claim 1, in which the self-checking code sequences are assigned to overlapping portions of the program in a relatively random fashion.

6. The method as in claim 5, further comprising:

determining whether a graph representing the assignment of self-checking code sequences to overlapping portions of the program is strongly connected; and

repeating step (b) if the graph is not strongly connected.

7. The method as in claim 1, in which the function that each self-checking code sequence is operable to calculate is a hash function.

8. The method as in claim 7, in which the hash function is invertible.

9. The method as in claim 8, in which the hash function is relatively lightweight.

10. The method as in claim 7, in which a first class of said self-checking code sequences calculates a first hash function and a second class of said self-checking code sequences calculates a second hash function that differs at least in part from the first hash function.

11. The method as in claim 10, in which a plurality of the first class of self-checking code sequences are customized, such that each of said plurality of customized self-checking code sequences differs, at least in part, from other self-checking code sequences in the first class.

12. The method as in claim 1, in which the self-checking code sequences are further operable to trigger a tamper response mechanism when an improper modification of the program is detected.

13. A non-transitory computer-readable medium storing instructions that, when executed by a processor, are configured to cause the processor to perform a method including:

calculating, utilizing a self-checking code sequence assigned to a first portion of a plurality of overlapping portions of a program, a function of the first portion, said portion containing a corrector having an assigned value chosen such that the function calculated by the self-checking code sequence results in a predefined value when the portion has not been improperly modified; and

triggering a tamper response mechanism if the functioned calculated by the self-checking code sequence does not result in the predefined value.

14. The non-transitory computer-readable medium as in claim 13, wherein the non-transitory computer-readable medium further stores instructions that, when executed by the processor, are configured to cause the processor to:

insert watermark values into the program.

15. The non-transitory computer-readable medium as in claim 13, wherein the function calculated utilizing the self-checking code sequence is a hash function.

16. The non-transitory computer-readable medium as in claim 15, which the hash function is invertible.

17. The non-transitory computer-readable medium as in claim 16, in which the hash function is relatively lightweight.