|
Cryptography, the use of codes and ciphers to protect secrets, began thousands of years ago. Until recent decades, it has been the story of what might be called classic cryptography — that is, of methods of encryption that use pen and paper, or perhaps simple mechanical aids. In the early 20th century, the invention of complex mechanical and electromechanical machines, such as the Enigma rotor machine, provided more sophisticated and efficient means of encryption; and the subsequent introduction of electronics and computing has allowed elaborate schemes of still greater complexity, most of which are entirely unsuited to pen and paper. The development of cryptography has been paralleled by the development of cryptanalysis — the "breaking" of codes and ciphers. The discovery and application, early on, of frequency analysis to the reading of encrypted communications has, on occasion, altered the course of history. Thus the Zimmermann Telegram triggered the United States' entry into World War I; and Allied reading of Nazi Germany's ciphers shortened World War II, in some evaluations by as much as two years. Until the 1970s, secure cryptography was largely the preserve of governments. Two events have since brought it squarely into the public domain: the creation of a public encryption standard (DES), and the invention of public-key cryptography. == Classical cryptography == The earliest known use of cryptography is found in non-standard hieroglyphs carved into monuments from the Old Kingdom of Egypt circa 1900 BC. These are not thought to be serious attempts at secret communications, however, but rather to have been attempts at mystery, intrigue, or even amusement for literate onlookers.〔 These are examples of still other uses of cryptography, or of something that looks (impressively if misleadingly) like it. Some clay tablets from Mesopotamia somewhat later are clearly meant to protect information—one dated near 1500 BCE was found to encrypt a craftsman's recipe for pottery glaze, presumably commercially valuable.〔(【引用サイトリンク】title=Cryptography in Ancient Civilizations )〕〔Kahn, David.'' The Codebreakers: A Comprehensive History of Secret Communication from Ancient Times to the Internet, Revised and Updated''. Scribner. New York, New York. 1996.〕 Later still, Hebrew scholars made use of simple monoalphabetic substitution ciphers (such as the Atbash cipher) beginning perhaps around 500 to 600 BC.〔("A Brief History of Cryptography." ''Cryptozine.'' 16 May 2008. )〕〔(Cohen, Fred. "A Short History of Cryptography." 1995. )〕 The ancient Greeks are said to have known of ciphers. The scytale transposition cipher was used by the Spartan military,〔 however it is disputed whether the scytale was for encryption, authentication, or avoiding bad omens in speech.〔Kelly, Thomas. “The Myth of the Skytale.” Cryptologia 22.3 (1998): 244–260.〕〔Lateiner, D. “Signifying Names and Other Ominous Accidental Utterances in Classical Historiography.” Greek, Roman, and Byzantine Studies 45.1 (2010): 35–57. Print.〕 Herodotus tells us of secret messages physically concealed beneath wax on wooden tablets or as a tattoo on a slave's head concealed by regrown hair, though these are not properly examples of cryptography ''per se'' as the message, once known, is directly readable; this is known as steganography. Another Greek method was developed by Polybius (now called the "Polybius Square").〔 The Romans knew something of cryptography (e.g., the Caesar cipher and its variations). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「History of cryptography」の詳細全文を読む スポンサード リンク
|