[Paper Review] Physical uncloneable function hardware keys utilizing Kirchhoff-law-Johnson-noise secure key exchange and noise-based logic

László B. Kish, Chiman Kwan|viXra|May 12, 2013

Physical Unclonable Functions (PUFs) and Hardware Security24 references4 citations

TL;DR

This paper proposes a novel class of physical uncloneable function (PUF) hardware keys based on Kirchhoff-law-Johnson-noise (KLJN) key exchange and noise-based logic (NBL), enabling unclonable, dynamically renewable encryption keys. It introduces an 'ultra-strong' PUF that achieves unconditional security through real-time key renewal via KLJN and one-time-pad-protected challenge/response using NBL, with tamper-resistant non-volatile storage for the initial key.

ABSTRACT

Weak physical uncloneable function (WPUF) encryption key means that the manufacturer of the hardware can clone the key but anybody else is unable to so that. Strong physical uncloneable function (SPUF) encryption key means that even the manufacturer of the hardware is unable to clone the key. In this paper, first we introduce a "ultra"-strong PUF with intrinsic dynamical randomness, which is not only not cloneable but it also gets renewed to an independent key (with fresh randomness) during each use via the unconditionally secure key exchange. The solution utilizes the Kirchhoff-law-Johnson-noise (KLJN) method for dynamical key renewal and a one-time-pad secure key for the challenge/response process. The secure key is stored in a flash memory on the chip to provide tamper-resistance and non-volatile storage with zero power requirements in standby mode. Simplified PUF keys are shown: a strong PUF utilizing KLJN protocol during the first run and noise-based logic (NBL) hyperspace vector string verification method for the challenge/response during the rest of its life or until it is re-initialized. Finally, the simplest PUF utilizes NBL without KLJN thus it can be cloned by the manufacturer but not by anybody else.

Motivation & Objective

• To address the vulnerability of traditional PUFs to cloning by the manufacturer by proposing a physically uncloneable key system.
• To achieve unconditional security in key exchange and storage using the Kirchhoff-law-Johnson-noise (KLJN) protocol.
• To enable dynamic key renewal during each use, ensuring fresh randomness and preventing replay attacks.
• To integrate tamper-resistant, zero-power non-volatile memory for secure key storage.
• To explore a hierarchy of PUF designs—from ultra-strong to simple—based on varying levels of physical uncloneability and implementation complexity.

Proposed method

• The system uses the KLJN protocol to perform unconditionally secure key exchange during each key usage, ensuring that the key is renewed with fresh randomness.
• A one-time-pad-secure key is stored in flash memory to protect the challenge/response phase, providing non-volatile, zero-power storage.
• Noise-based logic (NBL) is employed for hyperspace vector string verification in the challenge/response protocol, ensuring robustness against side-channel and cloning attacks.
• The ultra-strong PUF design combines KLJN-based key renewal with NBL-based verification, making cloning impossible even by the manufacturer.
• Simplified variants omit KLJN, relying only on NBL for challenge/response, making them cloneable by the manufacturer but not by external parties.
• The architecture leverages intrinsic thermal noise in resistors to generate unclonable, unpredictable physical characteristics for key generation.

Experimental results

Research questions

• RQ1 Can a PUF be constructed such that even the manufacturer cannot clone the key, ensuring true physical uncloneability?
• RQ2 Can unconditionally secure key exchange be achieved using thermal noise in resistors, enabling dynamic key renewal?
• RQ3 Can noise-based logic (NBL) be used to securely verify challenge/response interactions in a PUF system?
• RQ4 How can tamper-resistant, non-volatile, zero-power key storage be integrated into a PUF architecture?
• RQ5 What is the trade-off between security strength and implementation complexity in PUF designs based on KLJN and NBL?

Key findings

• The proposed ultra-strong PUF achieves unconditional security through KLJN-based key exchange, ensuring that the key is renewed with fresh randomness during each use.
• The system prevents cloning by the manufacturer due to the physical uncloneability of the thermal noise-based key generation and the one-time-pad protection of the challenge/response.
• The use of NBL enables secure, side-channel-resistant verification of the challenge/response, enhancing resilience against physical attacks.
• The integration of flash memory for key storage ensures non-volatile, tamper-resistant, and zero-power standby operation.
• The paper demonstrates a hierarchy of PUFs, from ultra-strong (KLJN + NBL) to simple (NBL only), offering scalable security and implementation trade-offs.
• The solution is theoretically unbreakable under the assumptions of the KLJN protocol and the one-time-pad, providing information-theoretic security.