A low area probing detector for power efficient security ICs

In this paper, a new concept of a low cost, Low Area Probing Detector (LAPD) is presented. Probing or microprobing is an attack technique against integrated circuits implementing security functions, such as OTP tokens or smartcards. It allows intercepting secrets from on-chip wires as well as injecting faults for other attacks. Microprobing is invasive as classified by Skorobogatov in 2005 and requires opening the microchip package as well as removing the passivation layer. While it may sound complicated and expensive, Maier and Nohl showed in 2012 that microprobing is feasible for low-budget adversaries. However, existing protection techniques against microprobing, such as active shields, redundancy of core components, or analog detection circuits containing large capacitors, are still expensive. The LAPD provides low-cost protection against microprobing. It measures minimal timing differences between on-chip wires caused by the capacitive load of microprobes. As a novelty, it is merely based on digital components and does not require analog circuitry, which reduces the required area and process steps compared to previous approaches.