A circuit provides a physically unclonable function. The circuit includes a first portion that provides a random value that varies according to an input to the circuit and a second portion that hashes the random value to provide an output value from the circuit. The first portion covers the second portion to prevent access to the random value. A breach of the first portions may alter operation of the first portion in a detectable manner. The first portion may cover a surface of a cube or parallelepiped. The first portion may be wrapped around a parallelepiped a plurality of times to cover each facet thereof from different directions. The output from the second portion may not intersect the first portion. The circuit may also include an external layer disposed on the first portion. The external layer may be glued to the first portion.