Differential Power Analysis of the Picnic Signature Scheme

This work introduces the first differential side-channel analysis of the Picnic Signature Scheme, an alternate candidate in the ongoing competition for post-quantum cryptography by the National Institute of Standards and Technology (NIST). We present a successful side-channel analysis of the underlying multiparty implementation of the LowMC block cipher (MPC-LowMC) and show how side-channel information can be used to recover the entire secret key by exploiting two different parts of the algorithm. LowMC key recovery then allows to forge signatures for the calling Picnic post-quantum signature scheme. We target the NIST reference implementation executed on a FRDM-K66F development board. Key recovery succeeds with fewer than 1000 LowMC traces, which can be obtained from fewer than 30 observed Picnic signatures.