A 47 F2/bit Charge-Sharing based Sequence-dependent PUF with a Permutative Challenge

Small sensor and actor nodes are often excluded from security mechanisms because of the lack of performance for cryptographic applications or the lack of a non-volatile memory to store the secret keys for such applications. Physical Unclonable Functions (PUFs) provide a good way for a secure key storage, but are also not necessarily lightweight in terms of area and power consumption. A PUF concept based on a capacitor array is described, which uses the a passive charge sharing technique and is able to accept a high number of challenges as input. By using pair building, an 8-stage array is able to derive up to 20160 bits of key material with an area use of $47\mathrm{F}^{2} /$bit in a 350nm CMOS technology.