UNIVERSAL SECURE TOKEN FOR OBFUSCATION AND TAMPER RESISTANCE

• US 20100115260A1
• Filed: 11/05/2008
• Published: 05/06/2010
• Est. Priority Date: 11/05/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Goyal, Vipul, Venkatesan, Ramarathnam
• Granted Patent: US 8,171,306 B2
• Time in Patent Office: Days
• US Class Current: 713/150
• CPC Class Codes: G06F 21/14 against software analysis or reverse engineering, e.g. by obfuscation
• CPC Class Codes: H04L 2209/16 Obfuscation or hiding, e.g. involving white box
• CPC Class Codes: H04L 9/3234 involving additional secure or trusted devices, e.g. TPM, smartcard, USB or software token network architectures or network communication protocols for supporting authentication of entities using an additional device in a packet data network H04L63/0853
• CPC Class Codes: H04L 9/3242 involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC

Abstract

Program obfuscation is accomplished with tamper proof token including an embedded oracle. A public obfuscation function can be applied to any program/circuit to produce a new obfuscated program/circuit that makes calls to the corresponding oracle to facilitate program execution. A universal circuit representation can be employ with respect to obfuscation to hide circuit wiring and allow the whole circuit to be public. Furthermore, the token or embedded oracle can be universal and stateless to enable a single token to be employed with respect to many programs.

Claims

1. A program obfuscation system, comprising:

a hardware token including a secret oracle component; and

an obfuscated program component, produced by a public obfuscation function corresponding to the secret oracle component, that includes queries to the oracle component to facilitate evaluation of the obfuscated program.

2. The system of claim 1, the token and corresponding oracle component are stateless to enable employment by multiple programs

3. The system of claim 1, the token and corresponding oracle component restrict queries to a fixed size.

4. The system of claim 1, the obfuscated program component is obfuscated as a universal circuit.

5. The system of claim 1, the oracle component includes a component that encrypts program input in response to one or more queries.

6. The system of claim 5, further comprising a component that injects a message authentication code within the input to facilitate tamper detection.

7. The system of claim 1, the oracle component includes a component that detects tampering with respect the obfuscated program and/or input.

8. The system of claim 1, the oracle component includes a component that receives encrypted input, evaluates a portion of the program, and returns encrypted results.

9. The system of claim 8, further comprising a component that generates message authentication code associated with the encrypted results to facilitate tamper detection.

10. The system of claim 8, further comprising a component that decrypts the results.

11. A method of program obfuscation, comprising:

receiving queries including encrypted information from one or more obfuscated universal circuit representations of programs; and

returning encrypted results to a querying program.

12. The method of claim 11, comprising receiving at least one input encryption query and returning an encrypted version of each input wire in the universal circuit.

13. The method of claim 12, further comprising outputting a message authentication code for each input wire of the universal circuit to facilitate identification of input alteration subsequent to encryption.

14. The method of claim 11, comprising receiving a gate evaluation query including encrypted versions if input wires and the gate and returning an encrypted version of the gate evaluation result.

15. The method of claim 11, further comprising receiving message authentication codes associated with the input wires and verifying input authentication utilizing the codes prior to evaluation.

16. The method of claim 11, further comprising receiving a query for decrypted output for a gate wire, decrypting the output, and returning the value.

17. The method of claim 16, further comprising authenticating encrypted data received with the query, and verifying that the wire is an output wire prior to returning the value.

18. A method of program obfuscation comprising:

acquiring a public obfuscation function; and

applying the function to a circuit representation of a program to generate an obfuscated universal circuit that includes queries to a tamper resistant oracle, employable by multiple programs, that includes corresponding functionality to facilitate evaluation of the obfuscated universal circuit.

19. The method of claim 18, further comprising acquiring the public obfuscation function from a particular user possessing the corresponding oracle.

20. The method of claim 18, further comprising acquiring the function from a token creation authority that creates the function and affords the corresponding oracle to a user.