Chris Christensen

Algebraic cryptanalysis of SMS4: gröbner basis attack and SAT attack compared

The SMS4 block cipher is part of the Chinese WAPI wireless standard. This paper describes the specification and offers a specification for a toy version called simplified SMS4 (S-SMS4). We explore algebraic attacks on SMS4 and S-SMS4 using Grobner basis attacks on equation systems over GF(2) and GF(28), as well as attacks using a SAT solver derived from the GF(2) model. A comparison of SAT and Grobner basis attacks is provided.

The usability of end user cryptographic products

Cryptography is an indispensable tool for securing data and for ensuring the privacy of communications such as web browsing and email. Although there are many practical utilities which can encrypt disks, file systems, and emails, these utilities are still not widely adopted by end users. One intention of cryptographic utilities is to enhance the confidentiality of information. From the security practitioners point of view, cryptography is a must for protecting sensitive data. System administrators and technical savvy people not only think many existing cryptography products are useful but also usable, at least to some extent. However, when viewed by majority of end users who do not have the technical background on cryptography, key and password management, authentication, and the complexity for using cryptography products can be the hurdles for making these utilities usable. This paper studies free and low-cost cryptographic products including encrypted flash drives, hard drives, file systems, and email systems to assess their usability. We also make recommendations for usable end-user cryptography.

The National Cash Register Company Additive Recovery Machine

Abstract During World War II, The National Cash Register Company built an additive recovery machine for the U.S. Navy. The machine was designed to attack the Imperial Japanese Navy cipher JN-25, which was a superenciphered code. This article describes how that machine, called “Fruit” by the British, implemented three methods of additive recovery: the known-word method, the difference method, and Knepperizing.

William Dean Wray (1910-1962) the Evolution of a Cryptanalyst

Abstract William Dean Wray was a cryptologist. He began his career with Naval Communications OP-20-GM in 1942 and rose through the cryptologic ranks until, at the time of his death, he was a senior official at the National Security Agency. We will outline the life and career of this remarkable person, mathematician, and cryptologist.

US Navy Cryptologic Mathematicians during World War II

Abstract Histories often marvel at the impressive mathematicians who were part of the World War II team at Bletchley Park, but what often goes unrecognized is that the United States Navy assembled a similarly impressive team. This paper recognizes some of the mathematicians who served at the Washington, D.C. Naval Communications Annex during World War II.

Review of The Theory That Would Not Die by Sharon McGrayne

With rare exception, I found this is a very entertaining and informative read with a flair for the dramatic. The book is very non-technical (only Bayes’ Rule itself appears, and early in the book at that) yet the reasoning behind the Rule resonates throughout. One appendix does give a numerical example generated from recent medical research. Generally following a chronological order, McGrayne introduces us not only to Bayes’ Rule and its surrounding controversy through the years, but also to the early pioneers in statistics (and their personalities!). Interspersing great historical events and the role of mathematicians, statisticians, and other scientists, McGrayne leads us through the fallow and fertile periods of Bayes’ Rule regarding its use and stature. The Theory That Would Not Die is organized in five sections, each comprised of a few chapters and covering significant time periods. With the exception of the final section, each section relates to some extent a rise and fall for the significance and applicability of Bayes’ Rule. The first section covers the greatest length of time and includes the greatest controversies surrounding the theorem. The story of Reverend Thomas Bayes and his ‘‘Inverse Probability of Cause’’ is developed. However, his work goes unpublished until posthumously done so by his friend Richard Price. Subsequently, Simon Laplace ‘‘rediscovers’’ Bayes’ Rule, gives it the formula seen today in countless textbooks, and applies it in astronomy and the social sciences. In the wake of Laplace’s death in 1827, McGrayne documents both the fall from grace of Laplace and the whole notion of a ‘‘subjective’’ prior probability and the beginnings of the ‘‘frequentist’’ approach to probability that lasts for over a century. In addition, McGrayne introduces the pioneers of modern statistics (Karl Pearson, R. A. Fisher, Jerzy Neyman) and their myriad accomplishments, internecine battles, and, most prominently, their disdain for Bayes. As this section concludes in the 1930’s, Bayes’ Rule faces extinction with scant supporters. The next section covers the Second World War years and the successful application of Bayes’ Rule in the efforts of Alan Turing, I. J. Good, and others in deciphering the Enigma and tracking U-Boats. Reading like a good novel, McGrayne captures the tension these men and other code breakers worked under to turn the

Review of In the Shadow of Pont du Gard: The Polish Enigma in Vichy France June 1940 to November 1942 by Zdzislaw J. Kapera

What happened to the Polish codebreakers after their escape from Poland in 1939? After hearing of their successes breaking Enigma during the 1930s, we usually hear only a few of the dramatic details of their fleeing to France, their years in France and Algeria, and the escape of Marian Rejewski and Henryk Zygalski through Spain to Britain. In the Shadow of Pont du Gard describes in detail the work of the Polish codebreakers in Vichy France from June 1940 until November 1942. As war with Germany loomed, on July 25, 1939, representatives of the Polish Cipher Bureau (Stefan Mayer, Guido Langer, Maksymilian Ciezki, and the codebreakers Marian Rejewski, Henryk Zygalski, and Jerzy Rozycki) met with representatives of the French (Gustave Bertrand and Henri Braquenie) and the British (Alastair Denniston, Dilly Knox, and Humphrey Sandwitch) at Pyry near Warsaw. It was at this meeting that the Poles presented their ‘‘gift’’ of their methods for breaking Enigma. Germany attacked Poland on September 1, 1939, and the Cipher Bureau crossed into Romania on September 17. After arriving in Bucharest, the Poles presented themselves to the British embassy but were ‘‘put off for a few days.’’ Then the Poles contacted the French, and arrangements were made for the Poles to travel to Paris to serve the Polish Armed Forces in the West.

Review of the 2011 Cryptologic History Symposium Cryptology in War and Peace: Crisis Points in History

As this review is being written, the 2011 Cryptologic History Symposium has just ended. This biennial gathering, which took place on Thursday and Friday, November 6 and 7, was a gathering of ‘‘Historians from the Center [for Cryptologic History], the Intelligence community, the defense establishment, and the military services, as well as distinguished scholars from American and foreign academic institutions, veterans of the profession, and the interested public [who gathered] for two days of reflection and debate on relevant and important topics from the cryptologic past.’’ [Symposium Announcement] The 2011 Symposium is the thirteenth (the second for the reviewer). The first five symposia were annual; originally one day was classified and one day was unclassified. Beginning with the sixth, the symposium became biennial, unclassified, and open to the public. The Symposium took place at the JohnsHopkinsUniversityApplied Physics Laboratory’s Kossiakoff Center in Laurel, Maryland, which is only a few miles from NSA headquarters and from Baltimore-Washington International (BWI) Thurgood Marshall Airport. The Kossiakoff Center is an excellent conference facility. Travel between the Kossiakoff Center, BWI, hotels, and restaurants would be difficult without a car. Dr. Kent Sieg of the Center for Cryptologic History was the Executive Director of the Symposium, and his work resulted in what seemed to be a flawless Symposium. Each day began with a light breakfast, a 30-minute opening address (which began at 8:00 am!), two morning sessions (which were separated by a time for refreshments), lunch (which included a presentation), two afternoon sessions (also separated by refreshments), and a plenary session at the end of the day (ending at 5:30 pm). Some sessions had concurrent panels. Registration cost

Lester Hill's Error-Detecting Codes

60 per day (

Review of The Secret Life of Bletchley Park: The World War II Codebreaking Centre and the Men and Women Who Were There

30 per day for students and is waived for presenters on the day of their presentation) and included breakfast, refreshments, and lunch—all of which were very good. Nearly 200 people participated in each day of the Symposium. The panels covered a wide spectrum of cryptologic history: