Cryptology
cryptology, étymologiquement science of the secrecy, can really be regarded as a science only recently. This science includes cryptography - the secret writing - and cryptanalyse - analysis of the latter.
One can say that cryptology is an old art and a new science: an art old bus used it already - the system is a particular case of the system of César which is an alphabetical shift -; a new science because it is only since years 1970 that it is an academic scientific research topic (to include/understand university). This discipline is related to many others, for example theory of the numbers, italgebra, complexity, information theory, or error correcting codes.
Synopsis |
Cryptography
- See too Cryptography
Cryptography is divided into two definitely differentiated parts:
- on the one hand cryptography with secret key, still called symmetrical
or traditional,
- in addition , known as
also asymmetrical or modern.
The first is oldest, one can make it go up withEgypt year 2000 front. J.- C. while passing by ; the second goes up with the article of W. Diffie and M. Hellman, New directions in cryptography gone back to 1976.
Both aim at ensuring the confidentiality of information, but cryptography with secret key requires as a preliminary the pooling between the recipients of certain information: key (symmetrical), necessary to coding like with the deciphering of the messages. Within the framework of cryptography with public key, it is not necessary any more. Indeed, the keys are then different, cannot result one from the other, and are used to make opposed operations, from where itasymmetry between the operations of coding and deciphering.
Although much more recent and in spite of enormous advantages - , exchange of keys... - cryptography with public key does not completely replace that with secret key, which for reasons speed of coding and sometimes of simplicity remains present. For this reason, let us announce the date of American ultimate on the matter, itAES : December 2001, which proves the still current vitality of symmetrical cryptography.
In the bestiary of the encryption algorithms, one can quote:
- for the symmetrical systems, it , itAES, Blowfish, IDEA, etc.
- for the asymmetrical systems, it , DSA-DH, ElGamal, them elliptic curves, etc.
Cryptanalyse
- See too Cryptanalyse
During this confidentiality is in the cryptanalyse. Obviously, since the existence of these secret codes, one sought with to break, to include/understand the coded messages although one is not the legitimate recipient, in other words to decipher. If the cryptanalyse of the system of César is easy (an index: statistical properties of the language, in French, it E is the most frequent letter), systems much more resistant were born. Some resisted a long time, that of Vigenère (The treaty in the secret manners of writing 1586) for example, not having been broken by Babbage that in the medium of XIXE century. Others, although not having be necessary exploitable, are not used any more because they are with the range of the modern computing powers. It is the case of with its key of 56 bits too judged short bus it can be found by exhaustive research (rough force).
In a bestiary of the cryptanalyse, it would almost be necessary to pass each system in review - not only each system, but also each implementation : for what is used the best armoured door if the wall which supports it is out of plywood? However, if one wants to really quote some techniques, one a:
- the differential cryptanalyse, Biham and Shamir (the S of ), 1991, systems;
- the linear cryptanalyse, Matsui, 1994, symmetrical systems;
- factorization, only average truth to decipher at the present time;
- the rough force, i.e. the systematic test of all the possible keys;
- and others still.
Other facets of cryptology
confidentiality is only one of the facets of cryptology. It also allows:
- authentification of a message: the assurrance that an individual is well the author of the coded message;
- integrity: one can check that the message was not handled without authorization or by error;
- proof with null disclosure of knowledge - for example of identity -, one can prove that one knows a secrecy without revealing it;
- and others, of which itanonymity and setting in pledge.
Essentially, it is cryptography with public key which provides the bases necessary to these aspects of cryptology.
A weapon of war
- See too History of cryptography
Cryptology was regarded very a long time as a weapon of war. To the IVE century before J.C., Énée the tactician, a Greek General, devotes a chapter to it in Comments on the defense of the fortified towns. One can quote the seat of the Small rock, where Antoine Rossignol (1600-1682) deciphers the messages which Huguenots besieged try to make leave. Richelieu learns there as well as Huguenots are famished and await the English fleet. This one will find with its arrival the French fleet, ready with the combat, as well as a dam blocking the access to the port.
Another example, the First World War, where office 40 - British cipher office - is illustrated particularly by deciphering one telegram envoy in January 1917 of Berlin to the German ambassador in Washington, which was to retransmit it in Mexico. They learn as well as Germany will launch out in a total underwater war and requires a military alliance, having to make it possible Mexico to recover New Mexico, Texas and Arizona. The English transmit this information to the United States, the telegram in light finds themselves published in the American newspapers the 1er March 1917. Following that, president Wilson does not have evil to obtain the agreement of the congress, the United States enter in war.
These examples illustrate well why the governments are careful as for the use of means cryptographic. Philip Zimmermann in made the experiment when it placed at the disposal its software of made safe transport, Pretty Good Privacy (PGP), in 1991. Violating the restrictions on export for the cryptographic products, PGP was very badly accomodated by the American government which opened an investigation in 1993 - given up in 1996, little before the government Clinton do not liberalize largely, at the dawn of the era of trade electronic the use of cryptography.
Various aspects of cryptology
- History of cryptography
- Cryptography (listing the principal algorithms and protocols)
- Symmetrical cryptography (or, with secret key)
- Quantum cryptography
References
Histories:
- Run of Cryptography, of the General Givierge, 1925.
- Elements of cryptography, of the Captain Roger Baudouin, 1939.
(With the difference of the foreign specialists, the French specialists publish at the time their know-how as regards cryptological analysis. This step as regards work with strategic potential is rather rare at the time to announce it.)
Contemporary:
- History of the secret codes, of S. Singh - JC Lattès, 1999.
- Run of cryptography, of G. Zémor - Cassini, 2000.
- The art of the secrecy, For science, file out-series, July-October 2002.
- The War of the secret codes, of D. Kahn - Inter editions, 1980 (transl. of The Codebreakers)
- Handbook of Applied Cryptography, of A.J. Menezes, P.C. van Oorschot and S.With. Vanstone - CRC Press, 1996. Completely on line!! (HTTP://www.cacr.maths.uwaterloo.ca/hac/)
- Decoding, of A. Muller - PUF, 1983 (cryptanalyse of the "traditional" systems)
- Secret writings, of A. Muller - PUF, 1971 (presentation of the "traditional" systems)
- Cryptography applied: protocols, algorithms and source codes out of C of B.Schneier (Second Edition), Vuibert, 2001
- Cryptography: theory and practical D. Stinson - ITP, 1996 (transl. of Cryptography theory and practice)
See too
Internal bonds
External bonds
- Ars Cryptographica Study of the secret messages of Antiquity at our days, and run of cryptology
- Run and software in remote loading
- FAQ over the length of the keys
- The FAQ of sci.French crypt
| Gate Cryptology - Reach the articles of Wikipédia concerning cryptology. |
