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Questions and Answers
What does the pair 'nt' encrypt to in the given example?
What does the pair 'nt' encrypt to in the given example?
Which method is used to jumble the order of letters in a message for the Rail Fence Cipher?
Which method is used to jumble the order of letters in a message for the Rail Fence Cipher?
Which statement is true regarding the security of transposition techniques?
Which statement is true regarding the security of transposition techniques?
In the context of a Rail Fence Cipher, what is the term used for the number of lines used during encryption?
In the context of a Rail Fence Cipher, what is the term used for the number of lines used during encryption?
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How is the plaintext divided in the second example with 'meet me at the school house'?
How is the plaintext divided in the second example with 'meet me at the school house'?
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What is the basic function of a row transposition cipher?
What is the basic function of a row transposition cipher?
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What happens to the white spaces in the plaintext during Rail Fence cipher encoding?
What happens to the white spaces in the plaintext during Rail Fence cipher encoding?
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What type of encryption technique is exemplified by 'n -> r' and 't -> q'?
What type of encryption technique is exemplified by 'n -> r' and 't -> q'?
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What is the primary mechanism used in a substitution technique?
What is the primary mechanism used in a substitution technique?
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In the Caesar cipher, what does the term 'shift' refer to?
In the Caesar cipher, what does the term 'shift' refer to?
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What is the purpose of modular arithmetic in the Caesar cipher?
What is the purpose of modular arithmetic in the Caesar cipher?
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If the letter 'A' is encrypted with a Caesar cipher using a shift of 3, what is the resulting letter?
If the letter 'A' is encrypted with a Caesar cipher using a shift of 3, what is the resulting letter?
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In the formula C = E(p) = (p + k) mod 26, what does 'k' represent?
In the formula C = E(p) = (p + k) mod 26, what does 'k' represent?
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What would be the ciphertext for the plaintext 'HELLO' using a Caesar cipher with a shift of 2?
What would be the ciphertext for the plaintext 'HELLO' using a Caesar cipher with a shift of 2?
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Which of the following statements is true about the Caesar cipher?
Which of the following statements is true about the Caesar cipher?
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How would the plaintext 'XYZ' be encrypted using a Caesar cipher with a shift of 1?
How would the plaintext 'XYZ' be encrypted using a Caesar cipher with a shift of 1?
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What is the correct formula for decrypting a message using the Caesar cipher?
What is the correct formula for decrypting a message using the Caesar cipher?
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Which of the following statements accurately describes the Playfair cipher?
Which of the following statements accurately describes the Playfair cipher?
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In the Playfair cipher, what is done if the plaintext has an odd number of letters?
In the Playfair cipher, what is done if the plaintext has an odd number of letters?
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What happens to the letters in a digraph if both letters are found in the same column of the Playfair cipher's matrix?
What happens to the letters in a digraph if both letters are found in the same column of the Playfair cipher's matrix?
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When two letters of a digraph are found in the same row of the Playfair cipher matrix, how are they encrypted?
When two letters of a digraph are found in the same row of the Playfair cipher matrix, how are they encrypted?
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Which pairing of letters in a Playfair digraph follows Rule 3 for encryption?
Which pairing of letters in a Playfair digraph follows Rule 3 for encryption?
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How is a keyword utilized in the Playfair cipher?
How is a keyword utilized in the Playfair cipher?
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What is the primary function of a digraph in the context of the Playfair cipher?
What is the primary function of a digraph in the context of the Playfair cipher?
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Study Notes
Classical Encryption Techniques
- Two main types: substitution and transposition
- Substitution replaces plaintext characters with other letters/numbers/symbols
- If plaintext is viewed as a bit sequence, substitution replaces plaintext bit patterns with ciphertext bit patterns
- Transposition rearranges plaintext letters without changing the characters
Substitution Techniques
- Replaces plaintext letters with other letters, numbers or symbols
- If plaintext is in bits, substitution involves replacing plaintext bit patterns with cipher text bit patterns
Caesar Cipher
- Earliest and simplest substitution method
- Each letter is replaced by a letter a fixed number of positions up or down the alphabet
- Example: with a shift of 1, A becomes B, B becomes C, etc.
- Named after Julius Caesar
- To cipher a given text, a shift value (integer) is needed to indicate how many positions the letters are shifted.
- Encryption can use modular arithmetic: A=0, B=1, ..., Z=25
- Encryption formula: E(p) = (p + k) mod 26
- Decryption formula: D(c) = (c - k) mod 26
- The shift 'k' value in the range of 1 to 25
- The alphabet is wrapped around (z+1 = a)
- Example: "amp" (shifted by 3) becomes "dps"
Playfair Cipher
- Best-known digraph substitution cipher.
- It treats plaintext pairs of two letters as units (digraphs)
- Uses a 5x5 matrix built using a keyword.
- Letters I and J are treated as one letter
- Encrypts two letters at a time following specific rules:
- If both letters are in the same column, take the letter below each in the column (wrapping from bottom to top)
- If both letters are in the same row, take the letter to the right of each (wrapping from right to left)
- If the letters are not in the same row or column, form a rectangle around them, taking the horizontal opposite letters for the cipher
- Example keyword "monarchy"
Transposition Techniques
- Rearranges plaintext letters, but doesn't change the letters themselves
- Simple arrangement change of letters
- Less secure than substitution, and easily recognizable
- Can be made more secure by multiple stages of transposition (more complex permutation, harder to decrypt)
Rail Fence Cipher
- A basic transposition cipher
- The plaintext is written in a zig-zag pattern across a series of rows, then read out (row by row).
- The number of rows is called the key.
- Example: (2 rail fence) "This is a secret message" Encrypted result: "TIHSSAESCRERTMSGSAME"
- More complex ciphers use more rows (rails).
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Description
Test your knowledge on classical encryption techniques, including substitution and transposition methods. Explore the workings of the Caesar cipher, its historical significance, and how it utilizes shifting characters in the alphabet. This quiz will challenge your understanding of these fundamental concepts in cryptography.
