Give the summary of the text using the key terms. HISTORICAL CRYPTOGRAPHY

HISTORICAL CRYPTOGRAPHY

Read the following words and word combinations and use them for understanding and translation of the text:

scribe- переписчик

inscription- надпись

substitution cipher- подстановочный шифр

parchment- пергамент

to wind- наматывать

length-wise- по длине

a transposition cipher- перестановочный шифр

to overtake- опережать

grid- решетка

offset- сдвинутый

gibberish- бессмысленный

to intercept- перехватывать

brute force method- подбор методом грубой силы

overconfidence- самонадеянность

to map- преобразовать

stepping switch- шаговый переключатель

renowned- прославленный

Ancient Egypt

The earliest known text containing components of cryptography originates in the Egyptian town Menet Khufu on the tomb of nobleman Khnumhotep II nearly 4,000 years ago. In about 1900 B.C. Khnumhotep's scribe drew his master's life in his tomb. As he drew the hieroglyphics he used a number of unusual symbols to obscure the meaning of the inscriptions. This method of encryption is an example of a substitution cipher, which is any cipher system which substitutes one symbol or character for another.

As the Egyptian culture evolved, hieroglyphic substitution became more common. This method of encryption was relatively easy to break for those who could read and write. There are several possibilities why the Egyptians would use the sacred nature of their religious rituals from common cryptography is that the scribes wanted to give a formal appearance to their writings. This seems to be very similar to formal complicated language used in any modern legal document. Egyptian cryptography could also have been a way for a scribe to impress others by showing that he could write at a higher level.

Greece

In about 500 B.C. the Spartans developed a device called Scytale, which was used to send and receive secret messages. The device was a cylinder in which a narrow strip of parchment was wound. The message was then written length-wise on the parchment. Once it was unwound the message on the strip of parchment became unreadable. To receive the message an identical cylinder was needed. It was only then that the letters would line up resulting in the original message.

The Scytale is an example of a transposition cipher, which is any cipher system that changes the order of the characters rather than changing the characters themselves. In today's standards, the Scytale would be very easy to decipher, however, 2,500 years ago the percent of people that could read and write was relatively small. The Scytale provided the Spartans a secure method of communication.

Rome

The earliest recorded military use of cryptography comes from Julius Caesar 2,000 years ago. Caesar, being commander of the Roman army, solved the problem of secure communication with his troops. The problem was that messengers of secret military messages were often overtaken by the enemy. Caesar developed a substitution cipher method in which he would substitute letters for different letters. Only those who knew the substitution used could decipher the secret messages. Now when the messengers were overtaken the secret messages were not exposed. This gave the Roman army a huge advantage during war.

Caesar typically just shifted his letters by some predetermined number. This number was the cipher key of his algorithm. A randomized order of substitution yields a much larger amount of security due to the larger amount of possible orderings.

Alberti-Vigenere Cipher

During the mid 1400s a man named Leon Battista Alberti invented an encryption system using a cipher disk. This was a mechanical device with sliding disks that allowed for many different methods of substitution. This is the base concept of a polyalphabetic cipher, which is an encryption method which switches through several substitution ciphers throughout encryption. Alberti never developed his cipher disk concept.

In the 1500s Blaise De Vigenere, following Alberti's polyalphabetic cipher style, created a cipher that came to be known as the Vigenere Cipher. The Vigenere Cipher works exactly like the Caesar except that it changes the key throughout the encryption process. The Vigenere Cipher uses a grid of letters that give the method of substitution. This grid is called a Vigenere Square or a Vigenere Table. The grid is made up of 26 alphabets offset from each other by one letter.

The method of changing from one key to another follows one simple pattern. The encryption key was chosen as a special secret word. The corresponding letter is then substituted for the plaintext character. This method is repeated through all characters of the key word. After all characters of the key word are used, the word is just repeated.

Jefferson Wheel Cipher

In the late 1700s, Thomas Jefferson came up with a cipher system very similar to the Vigenere Cipher except with higher security. His invention was 26 wheels with the alphabet randomly scattered on each wheel. The wheels were numbered and ordered with a specified order. This order is the key to the encryption algorithm.

To message to be encrypted on the wheels lining up is made on the wheels such that the message is present. The ciphertext is any other line besides the line containing the original message. The person decrypting the ciphertext must have the wheels in the proper order. As the ciphertext is made on the wheels, the plaintext is lined up somewhere else on the wheels. A visual scan can quickly result in finding the original text. There is an extremely small chance that two non-gibberish messages will emerge on the disk during decryption.

Zimmerman Telegram

In early 1917, during the early stages of World War I, British cryptographers encountered a German encoded telegram. This telegram is often referred to as the Zimmerman Telegram. These cryptographers were able to decipher the telegram, and in doing so they changed cryptanalysis history. Using this deciphered message, they were able to convince the United States to join the war.

The Zimmerman Telegram was a secret communication between the Foreign Secretary of the German Empire, Arthur Zimmerman, and the German ambassador in Mexico, Heinrich von Eckardt. The telegram contained an offer for Mexico to reclaim its territory of New Mexico, Texas, and Arizona if it joined the German cause.

Choctaw Codetalkers

As WWI went on, the United States had the continuing problem of the lack of secure communication. Almost every phone call made was intercepted by the Germans, leaving every move made by the allies known to the Germans. Army commander, Captain Lewis devised a plan that utilized American Indian languages. He found eight Choctaw men in the battalion and used them to talk to each other over radio and phone lines. Their language was valuable because ordinary codes and ciphers of a shared language can be broken, whereas codes based on a unique language must be studied extensively before beginning to decode them. Within 24 hours of using the Choctaw language as encryption, the advantage fell in favor of the United States. Within 72 hours, the Germans were retreating and the allies were in full attack.

Enigma Encryption Machine

At the end of World War I, Arthur Scherbius invented the Enigma, an electro-mechanical machine that was used for encryption and decryption of secret messages. Because of the numerous configurations, the Enigma was virtually unbreakable 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 became overconfident about their ability to encrypt secret messages. This overconfidence caused the downfall of the Enigma. Along with numerous German operator errors, the Enigma had several built-in weaknesses that Allied cryptographers exploited. The major weakness was that its substitution algorithm did not allow any letter to be mapped to itself. This allowed the Allied cryptographers to decrypt a vast number of ciphered messages sent by Nazi Germans.

Purple

While the Allied forces were focusing on cracking the German Enigma, the Japanese developed an encryption machine called Purple. In contrast to the Enigma's rotors, Purple was made using stepping switches commonly used for routing telephone signals. During the war, the Japanese were most efficient in destroying their encryption machines. Currently, not one complete Purple machine has been discovered.

Because the Japanese were so good at keeping their encryption methods secret, the United States cryptographers had a hard time decrypting their messages. William Friedman, a renowned cryptographer, and his team built a replica of Purple based only on the encrypted messages recovered. Because they had never seen a Purple machine and didn't know how it worked, this proved to be very difficult. Eventually the team figured out the encryption method used by Purple, and were able to build a different machine for the decryption of it. This advancement allowed the United States to access the Japanese diplomatic secrets in World War II.

Notes:

Khnumhotep – древнеегипетский высокопоставленный придворный вельможа.

B.C. (Before Christ) – до нашей эры.

Scytale – шифр Древней Спарты, прибор для перестано­вочного шифрования.

Choctaw – коренной народ США, проживавший изна­чально на юго-востоке.

Assignments

1. Translate the sentences from the texts into Russian in writing paying attention to the underlined words and phrases:

1. In about 1900 B.C. Khnumhotep's scribe drew his master's life in his tomb. As he drew the hieroglyphics he used a number of unusual symbols to obscure the meaning of the inscriptions.

2. The device was a cylinder in which a narrow strip of parchment was wound. The message was then written length-wise on the parchment.

3. The Scytale is an example of a transposition cipher, which is any cipher system that changes the order of the characters rather than changing the characters themselves

4. Only those who knew the substitution used could decipher the secret messages. Now when the messengers were overtaken the secret messages were not exposed.

5. A randomized order of substitution yields a much larger amount of security due to the larger amount of possible orderings.

6. There is an extremely small chance that two non-gibberish messages will emerge on the disk during decryption.

7. Because of the numerous configurations, the Enigma was virtually unbreakable with brute force methods.

8. The major weakness was that its substitution algorithm did not allow any letter to be mapped to itself.

2. Answer the following questions:

1. How does the substitution cipher work?

2. What is a Scytale?

3. What is a transposition cipher?

4. What idea underlies the Vegenere Cipher?

5. Why is it more difficult to break the code based on a unique language?

6. What is the Enigma known for?

3. Translate into English:

Криптография – тайнопись. Термин ввел Д. Валлис. Потребность шифровать и передавать шифрованные со­общения возникла очень давно. Так, еще в V-IV вв. до н. э. греки применяли специальное шифрующее устройство. По описанию Плутарха, оно состояло из двух палок одинако­вой длины и толщины. Одну оставляли себе, а другую от­давали отъезжающему. Эти палки называли скиталами. Ко­гда правителям нужно было сообщить какую-нибудь важ­ную тайну, тогда вырезали длинную и узкую, вроде ремня, полосу папируса, наматывали ее на свою скиталу, не остав­ляя на ней никакого промежутка, так чтобы 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 и без палки от­правляли адресату. Так как буквы на ней разбросаны в бес­порядке, то прочитать написанное он мог, только взяв свою скиталу и намотав на нее без пропусков эту полосу.

Аристотелю принадлежит способ дешифрования этого шифра. Надо изготовить длинный конус и, начиная с осно­вания, обертывать его лентой с шифрованным сообще­нием, постепенно сдвигая ее к вершине. В какой-то момент начнут просматриваться куски сообщения. Так можно оп­ределить диаметр скиталы.