A resistor mesh with distributed sensing points is provided in a security chip as an anti-tamper shield. An analog multiplexing circuit is configured to receive a pair of digital selection values created by an algorithm processing circuit, and produce a respective differential voltage formed by a pair of voltages obtained at a pair of selected sensing points within the resistor mesh corresponding to the pair of digital selection values. Each differential voltage is converted into a corresponding digital output value. An algorithm processing circuit is configured to receive a respective digital output value associated with each pair of digital selection values and derive a binary value based on a subset of the digital output values, wherein the binary value is unique to the security chip.