On demand code decryption

Patent metadata

Field	Value
Publication number	US-11336448-B2
Application number	US-201716313273-A
Country	US
Kind code	B2
Filing date	Jun 29, 2017
Priority date	Jun 29, 2016
Publication date	May 17, 2022
Grant date	May 17, 2022

Abstract

A system and a method for protecting code are provided. Extraction of code to be protected takes place during an object-to-object transformation and that code is replaced with fake binary code. The extracted code to be protected may then be encrypted or otherwise obscured and stored in a separate region of an object file. A prior source-to-source file transformation can be provided to isolate and mark the code to be protected, and to inject additional source code to handle later decryption.

First claim

The invention claimed is:

1. A method for protecting code, comprising carrying out an object-to-object file transformation, the object-to-object transformation comprising:
identifying, within an input object file to be encrypted, code to be protected;
extracting the identified code to be protected from the input object file;
to generate a first output object file, deleting and replacing, in the input object file, the identified code to be protected with a fake code; and
injecting the identified code to be protected into a second output object file,
wherein, prior to the object-to-object transformation, the method includes a source-to-source transformation comprising:
marking the identified code to be protected within an input source file; and
providing additional code to the input source file for a later decryption operation.

2. The method according to claim 1 , further comprising consolidating the first output object file and the second output object file in to a final object file.

3. The method according to claim 1 , wherein the source-to-source transformation further comprises isolating the identified code to be protected.

4. The method according to claim 1 , wherein the object-to-object transformation further comprises:
identifying relocation directions within the input object file;
excluding the relocation directions from replacement by the fake code.

5. The method according to claim 1 , wherein the fake code is selected to resemble real code.

6. The method according to claim 1 , wherein the object-to-object transformation further comprises encrypting the identified code to be protected.

7. A non-transitory computer readable medium storing computer-readable instructions that, when executed by processing circuitry, cause the processing circuitry to perform the method of claim 1 .

8. The method according to claim 1 , wherein the fake code is random code.

9. A system for protecting code, the system comprising:
processing circuitry that carries out an object-to-object file transformation by being configured to:
identify, within an input object file to be encrypted, code to be protected;
extract the identified code to be protected from the input object file;
to generate a first output object file, delete and replace, in the input object fie, the identified code to be protected with a fake code; and
inject the identified code to be protected into a second output object file,
wherein, prior to the object-to-object transformation, the processing circuitry is configured to perform a source-to-source transformation comprising, to perform said source-to-source transformation said processing circuitry is configured to
mark the identified code to be protected within an input source file; and
provide additional code to the input source file to provide instructions for a later decryption operation.

10. The system according to claim 9 , wherein the processing circuitry is further configured to consolidate the first output object file and the second output object file in to a final object file.

11. The system according to claim 9 , wherein to perform the source-to-source transformation, the processing circuitry is further configured to isolate the identified code to be protected.

12. The system according to claim 9 , wherein to perform the object-to-object transformation, the processing circuitry is further configured to:
identify relocation directions within the input object file; and
exclude the relocation directions from replacement by the fake code.

13. The system according to claim 9 , wherein the fake code is selected to resemble real code.

14. The system according to claim 9 , wherein to perform the object-to-object transformation, the processing circuitry is further configured to encrypt the identified code to be protected.

Assignees

• Nagravision Sa

Inventors

• Dore Laurent
• Piret Eric
• Belaidi Yasser
• Wyseur Brecht

Classifications

• G06F21/14 Primary

  against software analysis or reverse engineering, e.g. by obfuscation · CPC title

• G06F21/56

  Computer malware detection or handling, e.g. anti-virus arrangements · CPC title

• G06F21/602

  Providing cryptographic facilities or services · CPC title

• H04L9/32 Primary

  including means for verifying the identity or authority of a user of the system {or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials} · CPC title

• G06F2221/033

  Test or assess software · CPC title