Nagravision S.a.

Eric Piret

Brecht Wyseur

Laurent Dore

Yasser Belaidi

Laurent Doré

Wyseur Brecht

Belaïdi Yasser

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.

On demand code decryption

A system and a method for monitoring the integrity of code are provided. Dummy code is provided in an on demand decryption area of an object file while runtime code is provided elsewhere (and may be in the same object file or another object file). A compensation area is also provided which is initially blank. During execution, checksums can be calculated based on the result of an exclusive or (XOR) operation between contents of the on demand code decryption area and a compensation area such as a compensation area. As the runtime code populates the on demand code decryption area with the runtime code (potentially with the exception of areas masked to maintain integrity of relocation instructions allowed to remain in the dummy code) the compensation area is populated with the result of an XOR operation between the dummy code and the runtime code. As a result, the checksums will be the same throughout execution as long as integrity of the code has not been compromised.

Integrity of on demand code decryption

Growing community of inventors

Cheseaux-sur-Lausanne, Switzerland

Eric Piret