Improved Efficiency of PUF Response Reconstruction Method

Abstract

Physical unclonable function (PUF) represents modern element of cryptographic systems. Its advantage resides in generation of a unique identifier based on the physical structure of the device - hard to predict, difficult to clone. PUF usually require application of various constructions, in order to ensure security and reliability of the generated response. This paper describes an improved Code Word Masking method for reconstruction of a PUF response. Improved version is used for maximizing of a PUF response size and thus minimize requirements for an error correction code. The modification resides in repeated encoding of one response. The construction is performed two times, using two simple error correction codes. Such codes minimize complexity of the implementation and maximize utilization of the cells. The method is evaluated using implementation of the PUF in a 32-bit microcontroller. It is based on uninitialized values of static random access memory cells. The stability of the cells is analysed and just the most reliable cells are picked out. The implementation is more secure and effective, when compared to existing solutions. It was able to generate 140 bits using 512 PUF response bits without error, across various temperature and voltage levels. The security of the helper data does not depend on the statistical properties of the generated response.