Reliable secret key generation from physical unclonable functions under varying environmental conditions

Two methods are proposed to extract secret keys from ring oscillator (RO) physical unclonable functions (PUFs) under varying environmental conditions. A discrete cosine transform (DCT)-based RO PUF scheme that gives good results under nominal conditions is used in combination with these two methods, which are shown to be highly robust to environmental variations. The proposed methods significantly improve the secret-key size, reliability, uniqueness, and randomness results of existing RO PUF schemes under varying temperature and voltage conditions.