Dept. of  Electrical  and  Computer  Engineering, Texas A&M University

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Kirchhoff's-law-Johnson-(like)-noise (KLJN) secure key distribution

Unconditionally (information theoretically) secure key exchange scheme based on enhanced Johnson-noise, the Second Law of Thermodynamics and Kirchhoff's Law.

The last update in this page below is from November 14, 2014. A new KLJN page with the updates and the latest hot news is coming during the Fall of 2016.

Until then, check the Publication List (sections C-D-E) for news: 



Up to November 14, 2014:

We identified the experimental error leading to the giant information leak in the Gunn-Allison-Abbott (GAA) attack, see the next paragraph below. It is a fundamental error of engineering design. For the huge information leak results, they use a commercial cable attenuator, which is a voltage divider (T-element) breaking the single Kirchhoff-loop of the KLJN system into two coupled loops. Thus, what they measured was not a KLJN system. Another flaw in a Nature-based journal! Note: a fully built KLJN would not have been able to function due its built-in current/voltage comparison units at the two ends. Here is the link to the pdf file of our critical paper with these details (accepted for publication). click here.

- The
Gunn-Allison-Abbott (GAA) attack is published in (Nature) Scientific Reports. They also tested our breakthrough solution below (see the Entropy paper) and found that it protected even against their attack, see Equation (19) and the text around it. Note, they incorrectly say that alpha must be measured because all the resistors and the line parameters are public information in the KLJN system, and Alice and Bob knows them anyway. Concerning the rest of the GAA paper, all our former objections against the GAA attack holds, see those papers below. To read their Nature paper, click here.

Breakthrough: The famous old (Bergou)-Scheuer-Yariv wire resistance attack (for its correct treatment, see paper 13 below) is totally eliminated now. The new defense method, which is to increase the noise temperature of the smaller resistances, nullifies not only the (Bergou)-Scheuer-Yariv attack, but totally eliminates also the new, more efficient Second Law attack. Accepted for publication in Entropy. Click here for the paper. 

- Zoltan Gingl and Robert Mingesz gave a mathematical security proof showing that only Gaussian noises can be applied in the KLJN system, like it is in the original Johnson noise based scheme (resistor thermal noise without extra generators). PloS ONE (2014 April), Click here to read the paper

- Criticism-2 of the GAA attack paper. Due to the incorrect math/physics foundations of the Gunn-Allison-Abbott (GAA) attack system, we carried out the correct analysis  proving that it does not offer anything more efficient than the old comparison between the mean-square voltages at the cable ends, see the Kish-Scheuer paper below, in this page. We identified some of the possible experimental artifacts in GAA's work that could lead to the unphysical results. Our treatment shows that parasitic deterministic currents in the loop, non-Gaussianity, aliasing effects, non-linearities, etc, can affect the security practical KLJN systems if their design is poor. This paper is published. Click here to read the paper.

- Criticism-1 of the GAA attack paper. Proof that, in accordance with several laws of physics, no waves exist in a short cable at low frequencies. Note, this discussion is mostly irrelevant for security however concludes a historical open question.  The paper was motivated by the opposite claim in the GAA attack manuscript. This paper is published. Click here to read the paper.

- Our response to the Bennett-Riedel manuscript is published in PLOS ONE, click here

- The most general security proof based on the foundation of classical physics: the continuity of functions describing stable classical physical systems. With Claes Granqvist, published in Quantum Information Processing as invited paper, click here for the preprint and find the journal version by clicking on the DOI link there.

- Yessica: Efficient reduction of the bit error probability (10^-12 or less at practical conditions) with combined current and voltage monitoring, accepted for publication in Journal of Computational Electronics, click here

- Yessica: Error probability decays exponentially with increasing bandwidth or bit exchange duration,
accepted for publication in PLOS ONE, click here

Earlier news:

- Elias: Unconditionally secure Smart Grid (electrical power distribution), PLOS ONE, 2013,  click here   

- Physical Uncloneable Function (PUF) Non-Counterfeitable Hardware Keys, FNL, in press, click here

April 16, 2013. After one year that we had requested it, the Kish cypher Wikipedia page has been deleted,
   see our supporting comments at the Wikipedia Talk page, which finally triggered the deletion action. click here    

- Seven new KLJN systems with
strongly enhanced security and transient protocol for the non-ideal situations  click here

Wikipedia disclaimer: Up to April 16th, 2013, there was  a Wikipedia site called "Kish cypher", where even the name "Kish cypher" was incorrect  because this scheme is not a cypher but a secure key exchange protocol built on a specific physical system and its laws. That wiki page got fortunately deleted but its various versions are still circulating on the web and in wiki-based books. It was apparent that many of the contributors either have not read the papers or have not been able to follow them. Inspired by these events, a book shall be completed and published by World Scientific (expected at the end of 2014):

The KLN book cover and information

Relevant: on August 26, 2013, Scholarpedia published a brief introduction on KLJN  click here

Image of the simplified scheme in the Swedish magazine Ny Teknik (New Technology)
click to see/enlarge:

Jan_Melin's feature

Summary in Japanese (from SICE)

The fully protected KLJN scheme:

Continuous comparison of voltage and current
                    data at the wire ends.

- Status of the idealistic circuit scheme: Perfect security [16], Information theoretic level, that is, the security level is unconditional [16]; Security proofs for idealistic and various non-idealistic situations are given in papers [2,3,4,7,10,13,14].

- Status of the practical (non-idealistic) system. Without further defense: Imperfect security [16] (same as quantum encryption) but still Information theoretic [16] that is, unconditional security level; Security proofs for idealistic and various non-idealistic situations are given in papers [2,3,4,7,10,13,14].

Hacking is partially possible, (similar to Quantum Hacking,  click to watch video) 


- Privacy amplification can effectively remove the information leak [14]

- Even before privacy amplification, Alice and Bob has full control of the amount of information leak [10]

- They can discard the compromised bits, if necessary [10].

- Thus they are in the position to discard or manipulate the information Eve has [10].

- This is a new situation in physical cryptography and poses deep questions about the best policy for Alice and Bob. See below the remarks about information leak and, for a mathematical security analysis by Tamas Horvath, in the last section of paper [
10] and in paper [14].

- Some of the (other) unique properties of this secure key exchange scheme:

- Foundation of the security: The second law of thermodynamics: the impossibility to construct a perpetual motion machine of the second kind [2].

- Natural immunity against the man-in-the-middle-attack [3].

- Information leak via hacking are miniscule [7] and it is under full control by Alice and Bob who knows all the bits that Eve may have correctly extracted [10]. This property is very different from quantum communicator characteristics and it is only possible in classical physics

- Privacy amplification can always effectively remove the information leak and Perfect Security can be achieved even in non-idealistic system, see paper [14] below. This  is due to the extraordinary fidelity of the communication.

- Power lines and household power distribution networks can be utilized for (computationally) unconditional security, see paper [15] below.

Thus, all the households can be connected in a chain-like unconditionally secure network with a key-teleportation technology, see paper [4].

- Inexpensive, small, robust, low power consumption and it can be integrated on computer chips to unconditionally secure the information within computers, computer games, and hardware, see paper [11] click here.


19. Elias Gonzalez, Laszlo B. Kish, Robert Balog, Prasad Enjeti, "
Information theoretically secure, enhanced Johnson noise based key distribution over the smart grid with switched filters", submitted for publication, Click here to read it.

18. L.B. Kish, "Enhanced Secure Key Exchange Systems Based on the Johnson-Noise Scheme", accepted for publication. Click here to read it.

17. R. Mingesz, L.B. Kish, Z. Gingl, C.G. Granqvist, H. Wen, F. Peper, T. Eubanks, G. Schmera, "Unconditional security by the laws of classical physics", 
Metrol. Meas. Syst., Vol. XX (2013), No. 1, pp. 316, open access, Click here to read it.

R. Mingesz, L.B. Kish, Z. Gingl, C.G. Granqvist, H. Wen, F. Peper, T. Eubanks, G. Schmera, "Information theoretic security by the laws of classical physics", Plenary Talk at the 5th IEEE Workshop on Soft Computing Applications, 22-24 August (2012).

15. L.B. Kish, F. Pepper, "Information Networks Secured by the Laws of Physics", IEICE Transactions on Communinations E95-B (2012) 1501-1507; invited survey paper; includes the utilization of powerlines, phone landlines and interet wire lines to build robust secure networks with information theoretic (unconditional) security mesures. Click here to read it.

14. T. Horvath, L.B. Kish, J. Scheuer, "Effective Privacy Amplification for Secure Classical Communications", EPL (former Europhysics Letters)  94 (2011) 28002-p1 - 28002-p6. Click here to read it.

13. L.B. Kish and J. Scheuer, "Noise in the wire: the correct results for the Johnson (-like) noise based secure communicator", Physics Letters A 374 (2010) 2140-2142;  http://dx.doi.org/10.1016/j.physleta.2010.03.021 . Click here to read it.

12. L.B. Kish, "Absolutely Secure Communications by Johnson-like Noise and Kirchhoff's Laws", Invited review paper, Journal of the Society of Instrument and Control Engineers (SICE, Japan) 49 (2010) 212-216. Click here to read it

11. L.B. Kish, O. Saidi, "Unconditionally secure computers, algorithms and hardware, such as memories, processors, keyboards, flash and hard drives", Fluctuation and Noise Letters 8 (2008) L95-L98; click for the paper

10. L.B. Kish, T. Horvath, "Notes on Recent Approaches Concerning the Kirchhoff-Law-Johnson-Noise-based Secure Key Exchange", Physics Letters A 373 (2009) 901904; this paper is an extended security proof of the KLJN system and it is also a critical analysis of the paper by Pao-Lo Liu,  Physics Letters A 373 (2009) 901904 , "A new look at the classical key exchange system based on amplified Johnson noise",Click here to read it.

9. SPIE Newsroom article: "Unconditionally secure communication via wire" (October 2007, DOI: 10.1117/2.1200709.0863). Click here to read it.

8.  Featuring of the communicator prototype in the New Scientist magazine : "Noise keeps spooks out of the loop" by Jason D. Palmer, issue 2605, 23 May 2007, page 32. Click here to read it.

7.  Experimental demonstration of the secure communicator up to 2000 km range. Physics Letters A 372 (2008) 978-984. Click here for the manuscript.

This paper was the result of the Szegedin Whisper Project (2006) to develop and test the KLJN secure key exchange device.

KLJN Communicator (Network) cards            KLJN Communicator Team

Left to right: Robert Mingesz,  Laszlo Kish, Zoltan Gingl at the University of Szeged, Hungary, 12/15/2006; After the successful experimental demo of the  Szegedin Whisper Project  testing all known breaking attemps, including the man-in-the-middle attack during the very first run (quantum encryption is vulnerable against such), and thus proving superior-to-quantum security.

5.  Quick comparison table with usual quantum communication schemes; Table 4 from paper 4 below. (For dislaimer see in the paper).

4. Classical teleportantion network:  High-speed, one-step, whole-network key distribution with telecloning (teleportation) of the classical bits via a network of electrically isolated loops driven by Johnson-like noise,  Fluctuation and Noise Letters 6  (2006) C9-C21. Click here for the paper.

2. First manuscript about the Kirchhoff-loop-Johnson-like-noise cipher, Physics Letters A 352 (27 March 2006) 178-182. Click here for the paper.

1. Featuring of the first, that time unpublished, manuscript by  Science magazine: "Simple Noise May Stymie Spies Without Quantum Weirdness", by Adrian Cho (September 30, 2005). click here to read it.

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iv. Response to Feng Hao's paper "Kish's Key Exchange  Scheme is Insecure". Click here for the paper.

iii. Short response to
Scheuer-Yariv: "A Classical Key-Distribution System based on Johnson (like) noise - How Secure?", Physics Lett. A 359 (2006) 741744; Click here for the published paper.

ii. Longer (first) Response to Scheuer-Yariv: "A Classical Key-Distribution System based on Johnson (like) noise - How Secure?",physics/0601022; (http://arxiv.org/abs/physics/0602013). Click here for the manuscript.

i. Response to Terry Bollinger: "On the Impossibility of Keeping Out Eavesdroppers Using Only Classical Physics" and to Some Other Comments at Bruce Schneier's Blog Site. Click here for the text.

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Noise-based logic and computing. Click here to get to page.

Stealth Communication: Zero-Power Classical Communication and Zero-Quantum Quantum Communication, (published: Applied Physics Letters, 12/5, 2005). Click here for the slightly extended preprint of published paper.








Departmentof Electrical Engineering, Texas A&M University
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