A microcontroller SRAM-PUF

Key storage is a well-known security issue. Usually, keys are generated and then stored in an non-volatile memory (NVM). A promising alternative are the so-called physical unclonable functions (PUFs). These functions extract key material directly from manufacturing variabilities of a device. One example of such a PUF is the SRAM-PUF. It uses the power-up states of SRAM cells to generate an ID/key. In this paper we present an SRAM PUF which we implemented on a microcontroller using the internal SRAM blocks. Combined with a simple error correction code, namely the repetition code, we could reduce the error rates to small values. Using a repetition factor of 31 we reached a probability for one or more errors within a 2048bit key of lower than 7e-7 within a temperature range from 0C to 80C. The low costs and the simplicity of implementation makes the SRAM-PUF on a microcontroller an attractive alternative to common approaches.