Podcast
Questions and Answers
Which concept involves exchanging one letter for another?
Which concept involves exchanging one letter for another?
- Hill cipher
- Polyalphabetic substitution cipher (correct)
- Playfair cipher
- Auto key cipher
What type of substitution cipher involves using a key letter to shift the cipher alphabet for encryption?
What type of substitution cipher involves using a key letter to shift the cipher alphabet for encryption?
- Polyalphabetic substitution cipher
- Auto key cipher (correct)
- Playfair cipher
- Hill cipher
Which of the following ciphers involve using a 5x5 square of letters for encryption?
Which of the following ciphers involve using a 5x5 square of letters for encryption?
- Playfair cipher (correct)
- Auto key cipher
- Hill cipher
- Polyalphabetic substitution cipher
Which cipher technique involves matrix multiplication for encryption and decryption?
Which cipher technique involves matrix multiplication for encryption and decryption?
Which type of cipher relies on a keyword to determine the shifting of alphabets for encryption?
Which type of cipher relies on a keyword to determine the shifting of alphabets for encryption?
Which type of substitution cipher uses multiple alphabets to encrypt plaintext?
Which type of substitution cipher uses multiple alphabets to encrypt plaintext?
What is the defining characteristic of an Auto key cipher?
What is the defining characteristic of an Auto key cipher?
How is encryption performed in a Playfair cipher when two letters are in the same row of the secret key?
How is encryption performed in a Playfair cipher when two letters are in the same row of the secret key?
What is the key stream used in a Vigenere cipher?
What is the key stream used in a Vigenere cipher?
In an Auto key cipher, what value does the 3rd subkey take?
In an Auto key cipher, what value does the 3rd subkey take?
What happens in a Playfair cipher when two letters are neither in the same row nor in the same column?
What happens in a Playfair cipher when two letters are neither in the same row nor in the same column?
What makes Hill cipher different from a Playfair cipher?
What makes Hill cipher different from a Playfair cipher?
What is the main characteristic of a Polyalphabetic substitution cipher?
What is the main characteristic of a Polyalphabetic substitution cipher?
What is the characteristic of an Auto key cipher?
What is the characteristic of an Auto key cipher?
Which cipher is known for using a 5x5 grid of letters to encrypt messages?
Which cipher is known for using a 5x5 grid of letters to encrypt messages?
In the context of encryption, what does the Vigenere cipher rely on?
In the context of encryption, what does the Vigenere cipher rely on?
What differentiates Hill cipher from other ciphers?
What differentiates Hill cipher from other ciphers?
Which type of substitution cipher involves shifting letters based on a keyword?
Which type of substitution cipher involves shifting letters based on a keyword?
Flashcards
Autokey Cipher
Autokey Cipher
Uses a stream of subkeys, where each subkey is the previous plaintext character.
Playfair Cipher
Playfair Cipher
A 5x5 matrix containing 25 letters (I and J are combined) used as the secret key.
Polyalphabetic Substitution Cipher
Polyalphabetic Substitution Cipher
Each plaintext letter is encrypted with a different key, creating a 1:many mapping.
Encryption
Encryption
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Decryption
Decryption
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Cryptosystem
Cryptosystem
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Cryptanalyst
Cryptanalyst
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Substitution Cipher
Substitution Cipher
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Monoalphabetic Substitution Cipher
Monoalphabetic Substitution Cipher
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Additive Cipher
Additive Cipher
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Affine Cipher
Affine Cipher
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Combination Cipher
Combination Cipher
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Caesar Cipher
Caesar Cipher
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Vigenere Cipher
Vigenere Cipher
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Key Stream
Key Stream
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Key Stream
Key Stream
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Plaintext
Plaintext
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Ciphertext
Ciphertext
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Study Notes
Ciphers
- Autokey cipher: uses a stream of subkeys, where each subkey is used to encrypt the corresponding character in the plaintext.
- In Autokey cipher, the first subkey is predefined, and subsequent subkeys are the values of previous plaintext characters.
Playfair Cipher
- The secret key is a 5x5 matrix of 25 characters.
- Rules for encryption:
- If two letters are in the same row, the corresponding encrypted character is the next letter to the right.
- If two letters are in the same column, the corresponding encrypted character is the next letter below in the same column.
- If two letters are neither in the same row nor in the same column, the encrypted character is in its own row but in the same column as the other character.
Vigenere Cipher
- The key stream is the repetition of the initial secret key stream of length m.
- Example: Plaintext - ABCDEFGHK, Key - 0, 5, 8
Cryptography Basics
- Encryption: transforming plaintext into ciphertext using an encryption algorithm and a key.
- Decryption: transforming ciphertext back into plaintext using a decryption algorithm and a key.
- Cryptosystem: a set of rules for encryption and decryption, often using a device called a key.
- Cryptanalyst: a person who studies encryption and tries to find hidden meanings.
Substitution Ciphers
- Substitution: replacing plaintext characters with different ciphertext characters.
- Types:
- Monoalphabetic substitution cipher: 1:1 relationship between plaintext and ciphertext characters.
- Polyalphabetic substitution cipher: 1 to many relationships between plaintext and ciphertext characters.
Monoalphabetic Substitution Cipher
- Additive cipher: key value is added to plaintext, with numeric values ranging from 0 to 25.
- Example: Plain text - HELLO, Key - 15, Cipher text - WTAAD.
Affine Cipher
- Combines additive and multiplicative properties: C = (P + K) mod 26.
- Decryption: P = (C - K) mod 26.
Combination Cipher
- Combination of additive and multiplicative properties: C = [(P x K1) + K2] mod 26.
- Decryption: P = [(C - K2) x K1-1] mod 26.
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Description
Test your knowledge on various ciphers including Auto Key, Playfair, Vigenere, and Hill ciphers. Learn about the encryption and decryption techniques along with examples for each cipher.
