Cryptanalysis Chapter 2: English Letter Frequencies

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In a rail fence cipher, what happens to the plaintext?

The plaintext is encrypted using a one-time pad

The letters are rearranged in a zig-zag pattern (correct)

The plaintext is hidden within another message or file

The letters are substituted with different letters

What is a key characteristic of transposition ciphers?

They are unbreakable if the key is truly random and as long as the message

They alter the actual letters used in the plaintext

They use a one-time pad to encrypt the plaintext

They have the same frequency distribution as the original plaintext (correct)

What is the main advantage of the one-time pad cipher?

It is a type of transposition cipher

It is easy to implement and understand

It has a high level of security if the key is truly random and used only once (correct)

It can be easily broken using frequency analysis

What is a potential issue with the one-time pad cipher?

It is difficult to distribute the key securely Signup and view all the answers

What is steganography?

A method of hiding a message within another message or file Signup and view all the answers

What is a product cipher?

A cipher that combines two or more ciphers to increase security Signup and view all the answers

Which type of cryptanalytic attack involves selecting a ciphertext and obtaining the corresponding plaintext to attack the cipher?

Chosen ciphertext attack Signup and view all the answers

What is the mathematical definition of the Caesar Cipher encryption function?

C = E(p) = (p + k) mod (26) Signup and view all the answers

What is the key length for a monoalphabetic substitution cipher?

The key length is 26 Signup and view all the answers

What is the total number of possible keys for a monoalphabetic substitution cipher?

26! Signup and view all the answers

Which type of cryptographic attack relies on the nature of the algorithm and may involve knowledge of properties of the plaintext or even known plaintext-ciphertext pairs?

Cryptanalysis Signup and view all the answers

Which type of cryptographic attack involves attempting every possible key on a ciphertext until an intelligible translation into plaintext is obtained?

Brute-force attack Signup and view all the answers

What is the mathematical definition of the Caesar Cipher decryption function?

p = D(C) = (C - k) mod (26) Signup and view all the answers

Which type of cryptographic attack involves selecting a plaintext and obtaining the corresponding ciphertext to attack the cipher?

Chosen plaintext attack Signup and view all the answers

What is the meaning of the term 'unconditional security' in cryptography?

The cipher cannot be broken, regardless of the amount of computing power available, because the ciphertext provides insufficient information to uniquely determine the corresponding plaintext. Signup and view all the answers

What is the meaning of the term 'computational security' in cryptography?

The cost of breaking the cipher exceeds the value of the encrypted information, or the time required to break the cipher exceeds the useful lifetime of the information. Signup and view all the answers

What is the key used in the example of a row transposition cipher provided in the text?

4 3 1 2 5 6 7 Signup and view all the answers

What is the main drawback of steganography mentioned in the text?

It requires a lot of overhead to hide a relatively small amount of information. Signup and view all the answers

In the example of a rail fence cipher provided in the text, how many rows are used to write the message diagonally?

2 Signup and view all the answers

What is the main reason why ciphers using only substitutions or transpositions are not secure?

They can be easily broken using frequency analysis. Signup and view all the answers

What type of cipher is formed by combining a substitution cipher and a transposition cipher, as mentioned in the text?

A product cipher Signup and view all the answers

Which of the following is NOT a technique for hiding the existence of a message, as mentioned in the text's discussion of steganography?

Encrypting the message before hiding it Signup and view all the answers