Cryptography, Information Theory, and Error-Correction. Aiden A. Bruen. Читать онлайн. Newlib. NEWLIB.NET

Автор: Aiden A. Bruen
Издательство: John Wiley & Sons Limited
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Жанр произведения: Зарубежная компьютерная литература
Год издания: 0
isbn: 9781119582403
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The twentieth century ended with DES, the United States Data Encryption Standard, being phased out and replaced. In 1999, Rijndael, a block cipher developed by Joan Daemen and Vincent Rijmen was selected as the AES.5 AES is the current standard for symmetric cryptography [NIS19b]. Chapter 5 looks at these topics.

      Postquantum cryptography

      Less than 20 years after the adoption of AES, the United States is preparing for a postquantum world. See [NIS19f]. We will discuss this more in Section 4.12

      Blockchains

      Blockchains are being used increasingly because of their immutability. In April 2020, during the COVID‐19 pandemic, IBM used blockchains to help the health‐care industry. In [Wei20], Weiss writes that IBM is using blockchains to connect “pop‐up medical mask and equipment makers with hospitals.” They quote Mark Treshock, the IBM blockchain solutions leader for IBM healthcare and life sciences as saying, “It's the immutability component. If I am a supplier and I create a profile and include my information for onboarding as a new supplier, there's a qualification process I have to go through… It is done to determine if they are legitimate, ethical, that they comply with required laws and, in this case, with needed FDA certifications.” [Wei20]. We will discuss this more in Chapter 26.

      1 1 United States National Security Agency.

      2 2 Britain's Communications Electronics Security Group.

      3 3 di meaning two, graph meaning character or symbol.

      4 4 A poly‐alphabetic cipher uses several substitution alphabets instead of one.

      5 5 Published as Federal Information Processing Standard (FIPS) standard 197.

      Goals, Discussion In this chapter, we survey some historical ciphers which have been used since antiquity. (They are all symmetric ciphers. Public key ciphers were not invented until the 1970s and are discussed in Chapter 3.) Although the ciphers presented here are obsolete, they still provide good examples of cryptographic procedures. For example the Vigenère cipher, being a block cipher, is a forerunner of modern block ciphers such as Advanced Encryption Standard (AES). From these classical ciphers, we can also learn about various attacks in cryptography. This subject is pursued more fully in Chapter 7.

      New, Noteworthy We discuss the Vigenère cipher and show how it can be broken by finding the length of the keyword and then the keyword itself. We explain clearly the simple principles involved without getting bogged down in lengthy formulae. We also give a detailed but accessible description of the famous Enigma system used in World War II both from the mechanical and the mathematical point of view.

      While Julius Caesar was building his empire, he needed a method to transmit vital messages without risk of the enemy obtaining any crucial information. To achieve this goal, he employed one of the first known ciphering methods. The idea was to substitute each letter of the plain text with the letter appearing three spaces to the right in the alphabet, i.e. a is enciphered to D, b is enciphered to E, and z is enciphered to C (the alphabet wraps around). Thus, “six” is enciphered to “VLA.”

      For a numerical explanation, suppose we label a comma b comma ellipsis comma z by the numbers 0 comma 1 comma ellipsis comma 25. Using Caesar's key of three, the plain text message “six” is enciphered as follows:

six long right-arrow left-parenthesis 18 comma 8 comma 23 right-parenthesis long right-arrow Overscript k equals 3 Endscripts left-parenthesis 18 plus 3 comma 8 plus 3 comma 23 plus 3 right-parenthesis equals left-parenthesis 21 comma 11 comma 0 right-parenthesis right-arrow VLA Schematic illustration of Caesar cipher wheel.

      To decipher the message, reverse the operation (shift left by Скачать книгу