In this paper, we experimentally demonstrate that the commercial off the shelf flash memory chip can be used for Physical Unclonable Function (PUF), which provides important security primitive for device authentication. Since flash memory chips have high bit density, so random process variation is expected even with the identical manufacturing process. In order to exploit this inherent process variation, we used 'program-disturb' characteristics, which is a fundamental property of NAND flash memory. The experimental evaluation shows that the flash cells behave differently with applied program stress which results in unique, unclonable, and unpredictable signatures. We propose an algorithm to exploit this inherent variability to generate secret keys. The proposed method of PUF generation is fast, reliable and unique to a particular chip. We have experimentally evaluated the generated 32K-bit long key for uniqueness, randomness, and robustness. Since flash memory is ubiquitous in all electronic devices, our proposal is suitable for authentication, identification and counterfeit detection scheme for a wide range of electronic applications.
