| dc.description.abstract | This dissertation demonstrates three new types of attacks against the Kirchhoff-Law-Johnson-
Noise (KLJN) secure key exchanger.
The first attack type is based on compromised random number generators.
The first RNG attacks are deterministic. In the first attack, Eve knows both noises. We show
that Eve can quickly crack the bit via Ohm’s Law and one-bit powers, within a fraction of the
bit exchange period. In the second attack, Eve knows only Bob’s noise, so she can learn Bob’s
resistance value via Ohm’s Law and Alice’s resistance at the end of the bit exchange period. She
can also use a process of elimination.
The second RNG attacks are statistical. In the first attack, Eve has partial knowledge of Alice’s
and Bob’s noises. We show that Eve can crack the bit by taking the highest cross-correlation
between her noises and the measured noise in the wire, and by taking the highest cross-correlation between her noises and her evaluation of Alice’s/Bob’s noises. In the second attack, Eve has partial knowledge of only Alice’s noise. In this situation, Eve can still crack the bit, but after the bit exchange period.
The second attack type is based on thermodynamics. Previously, the KLJN scheme required
thermal equilibrium. However, Vadai, et al, in (Nature) Science Reports shows a modified scheme, where there is a non-zero thermal noise, yet the system resists all the known attacks. We introduce a new attack against their system, which utilizes coincidence events between the line current and voltage. We show that there is non-zero information leak toward the Eavesdropper. As soon as the thermal equilibrium is restored, the system becomes perfectly secure again.
The final attack type is based on the nonlinearity of the noise generators. We explore the effect
of total distortion at the second order, third order, and a combination of the second and third orders on the security of the KLJN scheme. It is demonstrated that a distortion as little as 1% results in a notable power flow, which leads to a significant information leak. We also show that decreasing the effective temperature results in the KLJN scheme approaching perfect security. | |
