@dooleyIntroductionRevolutionaryCipher2018
[!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.
Annotations¶
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Imported on 2023-02-02 1:42 pm¶
Relevant / important¶
[!quote|#a28ae5] Highlight In early August 1775 a young patriot from Newport, Rhode Island named Godfrey Wenwood received a request from his ex-wife, Mary Butler Wenwood. (Nagy 2013, pp. 169–171) It was to deliver a letter to a “Major Cane in Boston on his magisty’s service”. Wenwood was rather reluctant to deliver the letter, assuming, quite correctly, that Major Cane was a British officer stationed in Boston with access to General Gage, the commander of British forces in America. Instead he took it to a friend of his, a fellow patriot and a schoolmaster, who opened it and discovered three sheets of unintelligible writing. The letter was written in some kind of cipher.
Same storyy Graham used in his lecture
Page 1 [[2023-02-01#2:24 pm]]
[!quote|#a28ae5] Highlight called cryptography and with techniques to uncover the secret from the ciphertext, called cryptanalysis.
basically a back and forth between which side is better at encoding/decoding messages
Page 5 [[2023-02-01#2:35 pm]]
[!quote|#a28ae5] Highlight One could argue that a code is also a substitution cipher, just one with a larger number of substitutions
a very advanced version of the ancient ciphers Graham mentioned
Page 6 [[2023-02-01#2:36 pm]]
[!quote|#a28ae5] Highlight Note that because both the codewords and the words they represent are in ascending order, the cryptanalyst will instantly know that a codeword of 0823 must begin with an alphabetic sequence before “ce”, thus eliminating many possible codewordplaintext pairs.
too simple for most applications
Page 6 [[2023-02-01#2:37 pm]]
[!quote|#a28ae5] Highlight A 2-part code eliminates this problem by having two separate lists, one arranged numerically by codewords and one arranged alphabetically by the words and phrases the codewords represent. Thus one list (the one that is alphabetically sorted) is used for encoding a message and the other list (the one that is numerically sorted by codeword) is used for decoding messages.
adding a whole seperate layer to the code
Page 7 [[2023-02-01#2:38 pm]]
[!quote|#a28ae5] Highlight Substitution Ciphers
basically a ceasar cipher
Page 8 [[2023-02-01#2:43 pm]]
[!quote|#a28ae5] Highlight For added security, keys are changed periodically, so while the basic substitution cipher system remains the same, the key is different.
adding more depth, seems to be a trend
Page 9 [[2023-02-01#2:45 pm]]
[!quote|#a28ae5] Highlight nomenclator
talked about this in class
Page 10 [[2023-02-01#2:49 pm]]
[!quote|#a28ae5] Highlight ers of the plaintext message done according to a set of rules and guided by the key. Since the transposition is a permutation, there are n! different ciphertexts for an n-letter plainte
Page 10 [[2023-02-02#11:40 am]]
[!quote|#a28ae5] Highlight Since the transposition is a permutation, there are n! different ciphertexts for an n-letter plaintext message.
That is a lot. n to the factorial permutations that n * (n-1) * (n-2) until you reach one.
Page 10 [[2023-02-02#11:41 am]]
[!quote|#a28ae5] Highlight An incomplete columnar transposition cipher doesn’t require complete columns and so leaves off the null characters resulting in columns of differing lengths and making the system harder to cryptanalyze.
Page 10 [[2023-02-02#11:42 am]]
[!quote|#a28ae5] Highlight In a 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.
Page 11 [[2023-02-02#11:43 am]]
[!quote|#a28ae5] Highlight he first thing the cryptanalyst must know about a cryptogram is the language in which it is written.
Page 11 [[2023-02-02#11:43 am]]
[!quote|#a28ae5] Highlight Beginning in the early twentieth century, cryptanalysts began applying statistical tests to messages in an effort to discern patterns in more complicated cipher systems, particularly in polyalphabetic systems.
A more modern approach
Page 11 [[2023-02-02#11:44 am]]
[!quote|#a28ae5] Highlight And finally, with the advent of computers and computer cipher systems in the late twentieth century, cryptanalysts had to fall back on brute-force guessing to extract the key from a cryptogram or, more likely, a large set of cryptograms
All comes full circle
Page 11 [[2023-02-02#11:45 am]]
Definitions / concepts¶
[!quote|#2ea8e5] Highlight It must be that as soon as a culture has reached a certain level, probably measured largely by its literacy, cryptography appears spontaneously – as its parents, language and writing, probably also did. The multiple 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. Cultural diffusion seems a less likely explanation for its occurrence in so many areas, many of them distant and isolated
a very basic definition of cryptography
Page 5 [[2023-02-01#2:30 pm]]
[!quote|#2ea8e5] Highlight Steganography
search term
Page 5 [[2023-02-01#2:31 pm]]
[!quote|#2ea8e5] Highlight Cryptology, on the other hand, makes absolutely no effort to hide the presence of the secret message.
hidden in plain sight
Page 5 [[2023-02-01#2:33 pm]]
[!quote|#2ea8e5] Highlight A cryptologic system performs a transformation on a message – called the plaintext
How cryptology works
Page 5 [[2023-02-01#2:34 pm]]
[!quote|#2ea8e5] Highlight Substitution ciphers will replace each letter in a message with a different letter or symbol using a mapping called a cipher alphabet.
cipher 1
Page 8 [[2023-02-01#2:42 pm]]
[!quote|#2ea8e5] Highlight The 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.
cipher 2
Page 8 [[2023-02-01#2:42 pm]]
[!quote|#2ea8e5] Highlight symmetric key cipher system
when the same key is used at both ends
Page 9 [[2023-02-01#2:44 pm]]
[!quote|#2ea8e5] Highlight A substitution cipher that provides multiple substitutions for some letters but not others is a homophonic cipher system
Page 9 [[2023-02-01#2:47 pm]]
[!quote|#2ea8e5] Highlight dictionary cipher
Page 9 [[2023-02-01#2:47 pm]]
[!quote|#2ea8e5] Highlight For example, a codeword of 0450233 could specify page 045, column 02, and word 33 in that column
example of a dictionary cipher
Page 10 [[2023-02-01#2:48 pm]]
[!quote|#2ea8e5] Highlight Transposition ciphers transform the plaintext into ciphertext by rearranging the letters of the plaintext according to a specific rule and key.
definition
Page 10 [[2023-02-02#11:39 am]]
Agree¶
[!quote|#5fb236] Highlight Governments, the military, and people in business have desired to keep their communications secret ever since the invention of writing
Dont want data getting in the wrong hands. Especially in today's world
Page 5 [[2023-02-01#2:30 pm]]
[!quote|#5fb236] Highlight In the computer age, messages can be hidden inside images in documents simply by encoding the message into the bits of the image
A lot of modern game teasers hide secrets in dark backgrounds where people have to play with the image to get the hidden text out of it.
Page 5 [[2023-02-01#2:33 pm]]
[!quote|#5fb236] Highlight Because a code will likely have thousands of codeword-plaintext pairs, the cryptanalyst must slowly uncover each pair and over time create a dictionary that represents the code.
an exponential increase in security
Page 7 [[2023-02-01#2:39 pm]]
[!quote|#5fb236] Highlight Superencipherments add to the difficulty of cryptanalyzing a coded message.
instead of making the original code more complex they add different layers of the already complex code so its like unwrappings nested boxes
Page 7 [[2023-02-01#2:41 pm]]
[!quote|#5fb236] Highlight if a key is lost the underlying cipher system is not compromised and merely changing the key will restore the integrity of the cipher system
Makes it a lot quicker to switch between keys in the case of this
Page 9 [[2023-02-01#2:46 pm]]
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