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

Abstract

Secret keys are usually stored in a 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.