Using Power-Up SRAM State of Atmel ATmega1284P Microcontrollers as Physical Unclonable Function for Key Generation and Chip Identification

Secret keys are usually stored in an nonvolatile memory, which can be hard to secure. An alternative is to generate the keys “on-the-fly” by using the inherent uniqueness of a device based on the manufacturing process variations. This is realized by physical unclonable functions (PUFs). A promising approach is to construct an intrinsic PUF based on SRAM memory, since many electronic devices have embedded SRAM. However, using a SRAM as PUF requires the stability of the SRAM fingerprint under a wide variety of conditions, and the SRAM fingerprint must be unique. In this paper, we show that a 16Kbyte SRAM fingerprint contains sufficient entropy to uniquely identify each chip. In addition, if a postprocessing error correction is applied, the fingerprint can be used to generate a stable 4Kbit key.