Cryptography and Ciphers Redo 2

What is the main feature of a Caesar Shift Cipher?

• It substitutes each letter for another letter from a fixed alphabet.

• It uses a keyword for multiple substitution alphabets.

• It replaces a letter with another letter a fixed number of positions away in the alphabet.

• It rearranges the letters without changing them.

Answer explanation

The main feature of a Caesar Shift Cipher is that it replaces each letter with another letter a fixed number of positions away in the alphabet, making it a simple form of substitution cipher.

Which cipher uses multiple substitution alphabets based on a keyword?

• Simple Substitution Cipher

• Caesar Shift Cipher

• Playfair Cipher

• Vigenere Cipher

Answer explanation

The Vigenere Cipher uses multiple substitution alphabets derived from a keyword, allowing for more complex encryption than the Simple Substitution or Caesar Shift Ciphers, which use a single alphabet.

What is the main goal of Steganography?

• To scramble a message to make it unreadable to unauthorized parties.

• To hide the existence of the message itself.

• To replace pairs of letters with different pairs of letters.

• To use frequency analysis to break the encryption.

Answer explanation

The main goal of steganography is to hide the existence of the message itself, making it undetectable to unauthorized parties. This distinguishes it from other methods like encryption, which only scramble the content.

The Scytale is an example of what type of classical cipher?

• Substitution Cipher

• Transposition Cipher

• Homophonic Cipher

• Polygraphic Cipher

Answer explanation

The Scytale is a transposition cipher because it rearranges the letters of the plaintext to create the ciphertext, rather than substituting one letter for another. This method involves wrapping the message around a rod to encode it.

Which statement best describes the Pigpen Cipher?

• Polyalphabetic cipher using a shifting key.

• Homophonic cipher using multiple symbols per letter.

• Simple substitution cipher that uses symbols (or geometric shapes) instead of letters.

• Block cipher that operates on 64-bit blocks.

Answer explanation

The Pigpen Cipher is a simple substitution cipher that replaces letters with symbols or geometric shapes, making it easy to encode and decode messages without a shifting key or multiple symbols per letter.

What makes the Playfair Cipher different from a Simple Substitution Cipher?

• It uses a one-time pad.

• It encrypts digraphs (pairs of letters) instead of single letters.

• It requires a cylindrical device for encryption.

• It uses a new, random substitution for every character.

Answer explanation

The Playfair Cipher differs from a Simple Substitution Cipher by encrypting digraphs (pairs of letters) instead of single letters, making it more secure against frequency analysis.

What does a Simple Substitution Cipher replace?

• Single letters with a single, unique, corresponding plaintext letter.

• Single letters with a single, unique, corresponding ciphertext letter.

• Blocks of bits with a block of encrypted bits.

• Digraphs with digraphs.

Answer explanation

A Simple Substitution Cipher replaces single letters with unique ciphertext letters, ensuring each plaintext letter corresponds to one specific ciphertext letter, making the correct choice the second option.

Why is a Homophonic Substitution Cipher difficult to solve?

• Make the encryption process faster for computers.

• Obscure the frequency distribution of letters in the plaintext.

• Allow the use of non-alphabetic characters in the ciphertext.

• Encrypt an entire word or phrase as a single unit.

Answer explanation

A Homophonic Substitution Cipher replaces letters with multiple symbols, which obscures the frequency distribution of letters in the plaintext. This makes it harder for cryptanalysts to analyze patterns and break the code.

Blowfish is classified as a:

• Stream Cipher

• Block Cipher

• Transposition Cipher

• Substitution Cipher (Historical)

Answer explanation

Blowfish is classified as a Block Cipher because it encrypts data in fixed-size blocks (64 bits) using a symmetric key, making it suitable for secure data encryption.

The Playfair Cipher is an example of a:

• Simple Substitution Cipher

• Polyalphabetic Cipher

• Homophonic Substitution Cipher

• Polygraphic Substitution Cipher

Answer explanation

The Playfair Cipher encrypts pairs of letters, making it a Polygraphic Substitution Cipher. Unlike simple substitution ciphers that replace single letters, it substitutes groups of letters, enhancing security.