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  Компьютеры > Компьютерные технологии > Безопасность > Криптография
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A Brief History of Cryptography - compiled by Shireen Hebert

Cryptography, the science of encrypting and decrypting information, dates as far back as 1900 BC when a scribe in Egypt first used a derivation of the standard hieroglyphics of the day to communicate. Carl Ellison, Cryptography Timeline.

There are many notable personalities who participated in the evolution of Cryptography.  For example, “Julius Caesar (100-44 BC) used a simple substitution with the normal alphabet (just shifting the letters a fixed amount) in government communications”, and later, Sir Francis Bacon in 1623, who "described a cipher which now bears his name -- a biliteral cipher, known today as a 5-bit binary encoding.  He advanced it as a steganographic device -- by using variation in type face to carry each bit of the encoding”, Id.  Even one of our founding fathers, Thomas Jefferson, invented a wheel cipher in the 1790's, which would be redeveloped as the Strip Cipher, M-138-A, used by the US Navy during World War II.  Id

For all the historical personalities involved in the evolution of cryptography, it is William Frederick Friedman, founder of Riverbank Laboratories, cryptanalyst for the US government, and lead code-breaker of Japan’s World War II Purple Machine, who is “honored as the father of US cryptanalysis”.   Ellison, supra.  In 1918 Friedman authored The Index of Coincidence and Its Applications in Cryptography, which is still considered by many in this field as the premiere work on cryptograph written this century.  (Bruce Schneier, Forward to Applied Cryptography xv (Whitfield Diffie, John Wiley & Sons, Inc. 1996) (2nd ed. 1996). 

During the late 1920s and into the early 1930s, the US Federal Bureau of Investigation (FBI) established an office designed to deal with the increasing use of cryptography by criminals.  Ellison, supra.  At that time the criminal threat involved the importation of liquor.  Id. According to a report written in the mid-1930s by Mrs. Elizabeth Friedman, a cryptanalyst employed by the US government like her husband, William F. Friedman, the cryptography employed by bootleggers… "’are of a complexity never even attempted by any government for its most secret communications…. At no time during the World War, when secret methods of communication reached their highest development, were there used such involved ramifications as are to be found in some of the correspondence of West Coast rum running vessels.’"  Id.

Although cryptography was employed during World War I, two of the more notable machines were employed during World War II: the Germans’ Enigma machine, developed by Arthur Scherbius, and the Japanese Purple Machine, developed using techniques first discovered by Herbert O. Yardley.  Id.

In the 1970s, Dr. Horst Feistel established the precursor to today’s Data Encryption Standard (DES) with his ‘family’ of ciphers, the ‘Feistel ciphers’, while working at IBM’s Watson Research Laboratory. Id.  In 1976, The National Security Agency (NSA) worked with the Feistel ciphers to establish FIPS PUB-46, known today as DES. Ellison, supra.   Today, triple-DES is the security standard used by U.S. financial institututions.  Adam Back, "Why Crypto Software is Illegal to Export from the U.S.", 1998.  Also in 1976, two contemporaries of Feistel, Whitfield Diffie and Martin Hellman first introduced the idea of public key cryptography in a publication entitled "New Directions in Cryptography". Ellison,  supra.  Public key cryptography is what PGP, today's industry standard, uses in its software.

In the September, 1977 issue of The Scientific American, Ronald L. Rivest, Adi Shamir and Leonard M. Adleman introduced to the world their RSA cipher, applicable to public key cryptography and digital signatures. Ellison, supra. The authors offered to send their full report to anyone who sent them self-addressed stamped envelopes, and the ensuing international response was so overwhelming the NSA balked at the idea of such widespread distribution of cryptography source code. Id. When no response was made by the NSA as to the “legal  basis of their request”, distribution recommenced, and the algorithm was published in The Communications of the ACM the following year.  Id.  Today, one may access RSA Laboratories Site, to learn more about the RSA algorithm and its applications.

In the mid-1980s ROT13 was employed by USENET groups to prevent the viewing of “objectionable material [by] innocent eyes”, and soon thereafter, a 1990 discovery by Xuejia Lai and James Massey proposed a new, stronger, 128-bit key cipher designed to replace the aging DES standard:  IDEA.  Adam Back, supra. Called the International Data Encryption Algorithm, IDEA, this algorithm was designed to work more efficiently with “general purpose” computers used by everyday households and businesses.   Ellison, supra.

Concerned by the proliferation of cryptography, the FBI renewed its effort to gain access to plaintext messages of US citizens.  Ellison, supra.  In response, Phil Zimmerman released his first version of Pretty Good Privacy (PGP) in 1991 as a freeware product, which uses the IDEA algorithm.  Id.  PGP, a free program providing military-grade algorithms to the internet community, has evolved into a cryptographic standard because of such widespread use.  Ellison, supra.

The initial versions of PGP were geared towards the more computer literate individual, but to the individual nonetheless.  Phil Zimmerman could be compared to Henry Ford in his efforts to provide PGP to every home by making it free, and therefore, affordable.   Today, PGP's updated version is offered free to the public.  It can be downloaded at PGP's Freeware Page, located at the site of Network Associates, as PGP merged with Helix, McAffee, and Network General.  Also, for the consumer who needs technical support not offered using the freeware, PGP can also be purchased at a commercial site. 

Most recently, in 1994, Professor Ron Rivest, co-developer of RSA cryptography, published a new algorithm, RC5, on the Internet.  Ellison, supra.   Although he claims RC5 is stronger than DES, the algorithm is still relatively new.   Id.


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