@dooleyIntroductionRevolutionaryCipher2018
tags:: #Dooley #Annotations
[!info] - Cite Key: @dooleyIntroductionRevolutionaryCipher2018 - Link: Dooley - 2018 - Introduction – A Revolutionary Cipher.pdf - Abstract: Cryptology is the science of secret writing. It is made up of two halves; cryptography consists of the techniques for creating systems of secret writing and cryptanalysis encompasses the techniques of breaking them. Over the past 2500 years, cryptology has developed numerous types of systems to hide messages and subsequently a rich vocabulary in which to describe them. In this chapter we introduce the reader to the vocabulary of cryptology, explain the differences between codes and ciphers and begin the discussion of how to decipher an unknown message. - Bibliography: Dooley, JF. 2018 Introduction – A Revolutionary Cipher. In:. History of Cryptography and Cryptanalysis. History of Computing. Cham: Springer International Publishing. pp. 1–11. DOI: https://doi.org/10.1007/978-3-319-90443-6_1.
Annotations¶
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Definitions / concepts¶
[!quote|#a28ae5] Highlight Cryptology is the science of secret writing.
Page 1 2023-02-05#8:32 pm
[!quote|#a28ae5] Highlight cryptography consists of the techniques for creating systems of secret writing and cryptanalysis encompasses the techniques of breaking them.
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[!quote|#a28ae5] Highlight Steganography hides the very existence of the message
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[!quote|#a28ae5] Highlight cryptologic system performs a transformation on a message – called the plaintext.
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[!quote|#a28ae5] Highlight The transformation renders the plaintext unintelligible and produces a new version of the message – the ciphertext.
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[!quote|#a28ae5] Highlight encoding or enciphering the plaintext.
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[!quote|#a28ae5] Highlight A message in ciphertext is typically called a cryptogram.
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[!quote|#a28ae5] Highlight This is known as decoding or decrypting the ciphertext.
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[!quote|#a28ae5] Highlight A person who attempts to break cryptograms is a cryptanalyst.
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[!quote|#a28ae5] Highlight A code uses variable sized elements that have meaning in the plaintext language
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[!quote|#a28ae5] Highlight a cipher uses fixed sized elements like single letters or two- or three-letter groups that are divorced from meaning in the language
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[!quote|#a28ae5] Highlight the encoded message is then also enciphered so the codewords are enciphered when the message is transmitted. This is known as a superencipherment.
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[!quote|#a28ae5] Highlight Substitution ciphers will replace each letter in a message with a different letter or symbol using a mapping called a cipher alphabet.
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[!quote|#a28ae5] Highlight second type will rearrange the letters of a message, but will not substitute new letters for the existing letters in the message. These are transposition ciphers.
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[!quote|#a28ae5] Highlight single cipher alphabet for the entire message; these are known as monoalphabetic substitution ciphers
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[!quote|#a28ae5] Highlight more than one cipher alphabet to do the encryption are polyalphabetic substitution ciphers.
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[!quote|#a28ae5] Highlight All substitution ciphers depend on the use of a key to tell the user how to rearrange the standard alphabet into a cipher alphabet.
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[!quote|#a28ae5] Highlight same key is used to both encrypt and decrypt messages then the system is called a symmetric key cipher system.
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[!quote|#a28ae5] Highlight substitute two letters at a time, called a digraphic cipher system, or more than two, called a polygraphic cipher system.
Page 9 2023-02-05#9:11 pm
[!quote|#a28ae5] Highlight multiple substitutions for some letters but not others is a homophonic cipher system.
Page 9 2023-02-05#9:11 pm
[!quote|#a28ae5] Highlight avoid the use of a specific cipher alphabet and use a book to identify either individual letters or words. This is known as a book or dictionary cipher
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[!quote|#a28ae5] Highlight combination of a code and a cipher called a nomenclator.
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[!quote|#a28ae5] Highlight Transposition ciphers transform the plaintext into ciphertext by rearranging the letters of the plaintext according to a specific rule and key.
Page 10 2023-02-05#9:13 pm
[!quote|#a28ae5] Highlight columnar transposition. This comes in two forms, the complete columnar transposition and the incomplete columnar.
Good research topic.
Page 10 2023-02-05#9:14 pm
[!quote|#a28ae5] Highlight route transposition, one creates the standard rectangle of the plaintext, but then one takes off the letters using a rule that describes a route through the rectangle.
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Important¶
[!quote|#ffd400] Highlight This was the first successful cryptanalysis of a British cryptogram in the American Revolution.
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[!quote|#ffd400] Highlight A code always takes the form of a book where a numerical or alphabetic codeword is substituted for a complete word or phrase from the plaintext.
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Ideas/Thoughts¶
[!quote|#2ea8e5] Highlight human needs and desires that demand privacy among two or more people in the midst of social life must inevitably lead to cryptology wherever men thrive and wherever they write.
As soon as humans evloved in literature, cryptology was born. People wanted privacy and so they took to writing secret messages.
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[!quote|#2ea8e5] Highlight Governments, the military, and people in business have desired to keep their communications secret ever since the invention of writing. Spies, lovers, and diplomats all have secrets and are desperate to keep them as such.
This can still be seen in todays culture with encryption in coding, passwords and secret words.
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[!quote|#2ea8e5] Highlight Secret ink, microdots, and using different fonts on printed pages are all ways of hiding the message from prying eyes
Secret messages had to be secret from another persons eyes, many factors had to be taken into consideration as stated by Dooley.
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[!quote|#2ea8e5] Highlight Cryptology, on the other hand, makes absolutely no effort to hide the presence of the secret message. Instead it transforms the message into something unintelligible so that if the enemy intercepts the message they will have no hope of reading it.
Cryptology is not just hiding the message, rather it is the idea that the message can be seen easily but cannot be understood and needed to be decrypted.
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[!quote|#2ea8e5] Highlight concerned with both the creation of cryptologic systems, called cryptography and with techniques to uncover the secret from the ciphertext, called cryptanalysis.
The two main components of encoding
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[!quote|#2ea8e5] Highlight One could argue that a code is also a substitution cipher, just one with a larger number of substitutions.
It is important to understand that a code is different than a cipher.
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[!quote|#2ea8e5] Highlight But some codes are used merely for efficiency.
The discovery of encoding allows us to simplify other task. This can be related to texting nowadays where many words or phrases are shortened or encoded to allow for faster texting.
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[!quote|#2ea8e5] Highlight Superencipherments add to the difficulty of cryptanalyzing a coded message.
This idea of extra layering is important for many reasons as it acts as a fail safe if the first wall was to go down.
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[!quote|#2ea8e5] Highlight The codebook must also be kept physically secure, ideally locked up when not in use.
This is the target for many spies throughout history. Because the codebook holds all the information needed to decode a message, if the opposition was to get their hands on it, they could easily get advantage over their opponent.
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[!quote|#2ea8e5] Highlight The cipher alphabets may be standard alphabets that are shifted using a simple key. For example a shift of 7 results in,
Cool to explore the different ways cipher shifts were used in history.
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[!quote|#2ea8e5] Highlight security of the key is of paramount importance for cipher systems.
If the key is compremised the entire messaging system is revealed.
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[!quote|#2ea8e5] Highlight Management of the keys is a problem because a secure method must be used to transmit the keys to all users.
If the key is unable to be transferred to a user they will be unable to decipher the message.
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[!quote|#2ea8e5] Highlight governments that had the monopoly on cryptology for most of history
Having this monopoly gave great power so it was sought after.
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[!quote|#2ea8e5] Highlight word frequencies
Letter and word frequency was an easy way to decipher hidden messages.
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[!quote|#2ea8e5] Highlight cryptanalysts had to fall back on brute-force guessing to extract the key from a cryptogram
If all else falls brute force is the way to go.
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