w thaw18 - History of Cryptography, Książki IT

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//-->History of CryptographyAN EASY TO UNDERSTAND HISTORY OF CRYPTOGRAPHYContents1. Introduction2. Classical Encryptions (Ancient Times)3. Classical Encryptions (Middle Ages)The Cipher of Mary Queen of ScotsVigenère CiphersUesugi Cipher3466674. Modern Ciphers:Ciphers during World War I and the Emergence ofEncryption MachinesGerman Communication Cables Disconnected by the United KingdomZimmermann TelegramADFGVX CipherThe Birth of Enigma888895. Modern Ciphers:Encryptions in the Computer and Internet EraDES CipherPublic-Key CryptosystemRSA CipherDecrypting the DES CipherResponsive Action of Cipher Enhancements for SSL1010101112126. The Future of Encryption7. Conclusion:Enhancing the Effectiveness of Encryptions used for SSLReferences1314142© 2013 Thawte, Inc. All rights reserved. Thawte, the thawte logo, and other trademarks, service marks, and designs are registered or unregistered trademarks of Thawte,Inc. and its subsidiaries and affi liates in the United States and in foreign countries. All other trademarks are property of their respective owners.1. IntroductionEncryption and related technologies are widely and frequentlyused as a means of ensuring that information is secure, andtheir importance has been growing with the increasingly wide-spread utilization of the Internet.The use of encryption can be traced to as far back as about 3000B.C., during the Babylonian Era. Encryption technologies evolvedas they were used in military and political settings, but as a resultof the recent widespread use of the Internet and the dramaticincrease in the amount of information people come into contact intheir daily lives, the settings in which encryption technologies areapplied and implemented have increased, and they are now usedall around us in our daily lives.The history of encryption is the history of “the contest of wits” be-tween encryption developers and encryption code breakers. Eachtime a new encryption algorithm is created, it has been decrypted,and that in turn has led to the creation of a new encryption algo-rithm, and cycles of algorithm creation and decryption have beenrepeated to this day.This white paper presents a brief history of cryptography and howencryption-related technologies have evolved and will continueto evolve as well as the measures Internet users should considerwhen implementing modern encryptions.3© 2013 Thawte, Inc. All rights reserved. Thawte, the thawte logo, and other trademarks, service marks, and designs are registered or unregistered trademarks of Thawte,Inc. and its subsidiaries and affi liates in the United States and in foreign countries. All other trademarks are property of their respective owners.2. Classical Encryptions (Ancient Times)Hieroglyphics (pictograms used in ancient Egypt) inscribed ona stele in about 3000 B.C. are considered the oldest survivingSince the Caesar cipher involved the shifting of characters, it issometimes referred to as a “shift cipher”. If the alphabet con-sists of 26 letters, texts that have been encrypted by the Caesarcipher can be decrypted by trying 26 patterns. However, insteadof simply shifting the characters by a fixed number of places inthe alphabet, the sequence can be randomly rearranged, therebysignificantly increasing the number of possible patterns (in theThe “scytale cipher” was a form of encryption used in the citystate of Sparta in ancient Greece around the 6th century B.C. Itinvolved the use of a cylinder of a certain diameter around whicha parchment strip was wrapped, and the text was written on theparchment strip along the long axis of the cylinder. The methodof encryption was designed so that the recipient would be able toread it by wrapping the parchment strip around a cylinder of thesame diameter.Encryption methods like the “scytale cipher” that rely on rearrang-ing the sequence in which characters are read are referred to as“transposition ciphers”.The Caesar cipher, which appeared in the 1st century B.C., wasso named because it was frequently used by Julius Caesar, and itis a particularly prominent method of encryption among the greatnumber of encryption methods that emerged during the long his-tory of encryption.The Caesar cipher method of encryption involves replacing eachof the letters of the alphabet in the original text by a letter locateda set number of places further down the sequence of the lettersin the alphabet of the language. The sender and receiver agree inadvance to replace each letter of the alphabet in the text by a let-ter that is, for example, three letters further down in their alphabet.An encryption method that involves rearranging the sequence ofcharacters according to a specific rule such as that shown aboveis referred to as a “substitution cipher”. Substitution ciphers are awell-known encryption method, and they are the most commonlyused encryption method in the history of encryption. The modernencryption machine called “Enigma” described below made it pos-sible to apply the substitution cipher method with a higher level ofsophistication.Plain textcharacters(text that has notbeen encrypted)EncryptioncharactersSMKRATNGQJUDZLPVYOCWIBXFEHABCDEFGHIJKLMNOPQRSTUVWXYZexample of a 26-letter alphabet: 26 x 25 x 24 x …. = 400,000,000,000,000,000,000,000,000 patterns!) and making decryptiondramatically more difficult.example of encryption. Hieroglyphics were long considered im-possible to ever read, but the discovery and study of the RosettaStone in the 19th century was the catalyst that made it possible toread hieroglyphics.XYZABCDEF・・・・・・ABCDEFG HIFigure 14© 2013 Thawte, Inc. All rights reserved. Thawte, the thawte logo, and other trademarks, service marks, and designs are registered or unregistered trademarks of Thawte,Inc. and its subsidiaries and affi liates in the United States and in foreign countries. All other trademarks are property of their respective owners.The method of analysis that uses a reverse technique that takesadvantage of the fact that only one letter can be substituted foreach letter of the alphabet to decrypt “simple substitution ciphers”that depend on the letter substitution rule, e.g., the Caesar cipher,is known as “frequency analysis”.Frequency analysis uses the frequency of letters (e.g. The Englishalphabet has common frequency characteristics for letters listedbelow) to speculate unencrypted characters and identify theoriginal text:All of the encryption methods described above, including the sub-stitution cipher and transposition cipher, consist of an “encryptionalgorithm” and a “key”. The encryption algorithm refers to the rulesused for encrypting and decrypting text.Encryption algorithms refer to the rule for encryption, for example,by shifting characters in a substitution ciphers, or using a cylinderto wrap a parchment strip around and write the message in thetransposition cipher. The key refers to the number of places thecharacters are shifted in substitution ciphers and the diameter ofthe cylinder used for transposition ciphers. Since shifting charac-ters by five places in the Caesar cipher is different from shiftingthem by four places, it means using different “keys”.•The letter “e” is the most frequently used letter. (Figure 2)•The letter “u” almost always follows the letter “q”.•The words “any”, “and”, “the”, “are”, “of”, “if”, “is”, “it”, and “in”are very common.0.140.120.1Relative frequency0.080.060.040.02a b c d efg hijkl m n o p qletterrstu v w xyzFigure 25© 2013 Thawte, Inc. All rights reserved. Thawte, the thawte logo, and other trademarks, service marks, and designs are registered or unregistered trademarks of Thawte,Inc. and its subsidiaries and affi liates in the United States and in foreign countries. All other trademarks are property of their respective owners. [ Pobierz całość w formacie PDF ]