Week 06 Flashcards
Scytale Cipher
Scytale Cipher
A transposition cipher where a strip of text is wound around a rod, and the message is read by re-wrapping it around a rod of the same diameter.
Vigenere Cipher
Vigenere Cipher
A polyalphabetic substitution cipher that uses a keyword to shift letters in the plaintext, making it more secure by using multiple Caesar shifts throughout the message.
polyalphabetic substitution cipher
polyalphabetic substitution cipher
A polyalphabetic substitution cipher uses multiple substitution alphabets to encrypt a message, changing the letter mappings throughout the text to make it more resistant to frequency analysis attacks.
frequency analysis
frequency analysis
Frequency analysis is a cryptanalysis technique that studies the frequency of letters or groups of letters in a ciphertext to identify patterns and decipher the encrypted message, exploiting the natural frequency of letters in a language.
block cipher vs stream cipher
block cipher vs stream cipher
A block cipher encrypts data in fixed-size blocks (e.g., 128 bits) and processes one block at a time, while a stream cipher encrypts data one bit or byte at a time, making it more suitable for real-time encryption where data size varies.
keystream generators
keystream generators
Keystream generators produce a sequence of pseudorandom bits (keystream) used in stream ciphers to combine with plaintext, typically using XOR, to create ciphertext and ensure secure encryption.
5 Block Cipher Modes
5 Block Cipher Modes
- Electronic Codebook
- Cipher Block Chaining (CBC)
- Cipher Feedback (CFB)
- Output Feedback (OFB)
- Counter (CTR)
Block cipher attributes
Block cipher attributes
Confusion
*Carried out through substitution
2. Diffusion
*Carried out through transposition
Vernam Cipher
Vernam Cipher
The Vernam Cipher, also known as the One-Time Pad, is a stream cipher where each bit or character of the plaintext is XORed with a random key of the same length, providing theoretically unbreakable encryption if the key is truly random, used only once, and kept secret.
Running Key Cipher
Running Key Cipher
The running key cipher is a polygraphic substitution cipher that encrypts a plaintext message by shifting each letter according to the corresponding letter of a long key text, making it as secure as the randomness and length of the key allow.
