Computer Science. The English Language Perspective - Беликова (1176925), страница 32
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Thistelegram is often referred to as the Zimmerman Telegram.These cryptographers were able to decipher the telegram, andin doing so they changed cryptanalysis history. Using thisdeciphered message, they were able to convince the UnitedStates to join the war.The Zimmerman Telegram was a secret communicationbetween the Foreign Secretary of the German Empire, ArthurZimmerman, and the German ambassador in Mexico, Heinrichvon Eckardt. The telegram contained an offer for Mexico toreclaim its territory of New Mexico, Texas, and Arizona if itjoined the German cause.Choctaw CodetalkersAs WWI went on, the United States had the continuing problemof the lack of secure communication. Almost every phone callmade was intercepted by the Germans, leaving every movemade by the allies known to the Germans.
Army commander,Captain Lewis devised a plan that utilized American Indianlanguages. He found eight Choctaw men in the battalion andused them to talk to each other over radio and phone lines.Their language was valuable because ordinary codes andciphers of a shared language can be broken, whereas codesbased on a unique language must be studied extensively beforebeginning to decode them.
Within 24 hours of using theChoctaw language as encryption, the advantage fell in favor ofthe United States. Within 72 hours, the Germans were retreatingand the allies were in full attack.189Enigma Encryption MachineAt the end of World War I, Arthur Scherbius invented theEnigma, an electro-mechanical machine that was used forencryption and decryption of secret messages.
Because of thenumerous configurations, the Enigma was virtuallyunbreakable with brute force methods.It wasn't until World War II that the Enigma gained its fame.Due to the Enigma's statistical security, Nazi Germany becameoverconfident about their ability to encrypt secret messages.This overconfidence caused the downfall of the Enigma. Alongwith numerous German operator errors, the Enigma hadseveral built-in weaknesses that Allied cryptographersexploited.
The major weakness was that its substitutionalgorithm did not allow any letter to be mapped to itself. Thisallowed the Allied cryptographers to decrypt a vast number ofciphered messages sent by Nazi Germans.PurpleWhile the Allied forces were focusing on cracking the GermanEnigma, the Japanese developed an encryption machine calledPurple. In contrast to the Enigma's rotors, Purple was madeusing stepping switches commonly used for routing telephonesignals. During the war, the Japanese were most efficient indestroying their encryption machines. Currently, not onecomplete Purple machine has been discovered.Because the Japanese were so good at keeping their encryptionmethods secret, the United States cryptographers had a hardtime decrypting their messages. William Friedman, a renownedcryptographer, and his team built a replica of Purple based onlyon the encrypted messages recovered.
Because they had neverseen a Purple machine and didn't know how it worked, thisproved to be very difficult. Eventually the team figured out theencryption method used by Purple, and were able to build adifferent machine for the decryption of it. This advancementallowed the United States to access the Japanese diplomaticsecrets in World War II.190Notes:Khnumhotep – древнеегипетский высокопоставленныйпридворный вельможа.B.C. (Before Christ) – до нашей эры.Scytale – шифр Древней Спарты, прибордляперестановочного шифрования.Choctaw – коренной народ США, проживавшийизначально на юго-востоке.Assignments1. Translate the sentences from the texts into Russian inwriting paying attention to the underlined words andphrases:1. In about 1900 B.C.
Khnumhotep's scribe drew hismaster's life in his tomb. As he drew the hieroglyphicshe used a number of unusual symbols to obscure themeaning of the inscriptions.2. The device was a cylinder in which a narrow strip ofparchment was wound. The message was then writtenlength-wise on the parchment.3. The Scytale is an example of a transposition cipher,which is any cipher system that changes the order of thecharacters rather than changing the charactersthemselves4.
Only those who knew the substitution used coulddecipher the secret messages. Now when themessengers were overtaken the secret messages werenot exposed.5. A randomized order of substitution yields a much largeramount of security due to the larger amount of possibleorderings.1916. There is an extremely small chance that two nongibberish messages will emerge on the disk duringdecryption.7. Because of the numerous configurations, the Enigmawas virtually unbreakable with brute force methods.8. The major weakness was that its substitution algorithmdid not allow any letter to be mapped to itself.2. Answer the following questions:1.2.3.4.5.How does the substitution cipher work?What is a Scytale?What is a transposition cipher?What idea underlies the Vegenere Cipher?Why is it more difficult to break the code based on aunique language?6.
What is the Enigma known for?3. Translate into English:Криптография – тайнопись. Термин ввел Д. Валлис.Потребность шифровать и передавать шифрованныесообщения возникла очень давно. Так, еще в V-IV вв. до н. э.греки применяли специальное шифрующее устройство. Поописанию Плутарха, оно состояло из двух палокодинаковой длины и толщины. Одну оставляли себе, адругую отдавали отъезжающему. Эти палки называлискиталами. Когда правителям нужно было сообщитькакую-нибудь важную тайну, тогда вырезали длинную иузкую, вроде ремня, полосу папируса, наматывали ее насвою скиталу, не оставляя на ней никакого промежутка, такчтобы вся поверхность палки была охвачена этой полосой.Затем, оставляя папирус на скитале в том виде, как он есть,писали на нем все, что нужно, а написав, снимали полосу ибез палки отправляли адресату. Так как буквы на ней192разбросаны в беспорядке, то прочитать написанное он мог,только взяв свою скиталу и намотав на нее без пропусковэту полосу.Аристотелю принадлежит способ дешифрования этогошифра.
Надо изготовить длинный конус и, начиная соснования, обертывать его лентой с шифрованнымсообщением, постепенно сдвигая ее к вершине. В какой-томомент начнут просматриваться куски сообщения. Такможно определить диаметр скиталы.4. Give the summary of the text using the key terms.MODERN ENCRYPTIONRead the following words and word combinations and usethem for understanding and translation of the text:one-time pad – блокнот одноразового использованияto withstand - противостоятьprior to...
- перед чем-либоto be referred to as... - называтьсяflaw - ошибкаstaggering - ошеломляющийpower (зд.) - степеньconventional computers — традиционные компьютерыto listen in - подслушатьkey distribution problem — задача распределения ключейUntil the 1990s, cryptology was based on algorithms -- amathematical process or procedure. These algorithms are usedin conjunction with a key, a collection of bits (usually numbers).Without the proper key, it's virtually impossible to decipher anencoded message, even if you know what algorithm to use.The "one-time pad" encryption algorithm was invented in theearly 1900s, and has since been proven as unbreakable. The one193time pad algorithm is derived from a previous cipher calledVernam Cipher, named after Gilbert Vernam.
The VernamCipher was a cipher that combined a message with a key readfrom a paper tape or pad. The Vernam Cipher was notunbreakable until Joseph Mauborgne recognized that if the keywas completely random the cryptanalytic difficultly would beequal to attempting every possible key. Even when trying everypossible key, one would still have to review each attempt atdecipherment to see if the proper key was used.
Theunbreakable aspect of the one-time pad comes from twoassumptions: the key used is completely random; and the keycannot be used more than once. The security of the one-timepad relies on keeping the key 100% secret. The one-time pad istypically implemented by using a modular addition (XOR) tocombine plaintext elements with key elements. The key usedfor encryption is also used for decryption.
Applying the samekey to the ciphertext results back to the plaintext.If any non-randomness occurs in the key of a one-time pad, thesecurity is decreased and thus no more unbreakable. Numerousattempts have been made to create seemingly random numbersfrom a designated key. These number generators are calledPseudo-Random Number Generators (PRNGs) because theycannot give a completely random number stream. Even thoughthe security of a PRNG is not 100% unbreakable, it can providesufficient security when implemented correctly. PRNGs thathave been designated secure for cryptographic use are calledCryptographically Secure Pseudo-Random Number Generators(CSPRNGs).
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