Crypto U4, Block Cipher, Cipher Block Chaining Mode (CBC)

jjanesko
Note by , created almost 6 years ago

IYM002 (Unit 4 - Symmetric Crypto) Note on Crypto U4, Block Cipher, Cipher Block Chaining Mode (CBC), created by jjanesko on 03/04/2013.

Eye 277
Pin 11
Balloon left 0
Tags
jjanesko
Created by jjanesko almost 6 years ago
Crypto U1, Basic Principles
jjanesko
Crypto U3, Theoretical vs. Practical Security
jjanesko
Crypto U2, Crypto design principles
jjanesko
SAT Exam 'Word of the Day' Set 2
SAT Prep Group
GCSE AQA Physics Unit 2 Flashcards
Gabi Germain
Crypto U4, Block Cipher, Cipher Feedback Mode (CFB)
jjanesko
Crypto U4, Block Cipher, Electronic Codebook Mode (ECB)
jjanesko
Crypto U4, Block Cipher, Counter Mode
jjanesko
Crypto U4, Stream Cipher
jjanesko
Crypto: U3 & U4 Flashcards (by Mohamed Ahmed Enab)
jjanesko

Page 1

Encryption Start with an initialization vector (IV). XOR the IV with the first block of plaintext. Pass the result and the key to the encryption function. The result of the operation is the first ciphertext block. XOR the resulting ciphertext block with the next plaintext block. Pass the result and the key to the encryption function. The result of the operation is the next ciphertext block. Go back to step 5 and repeat until there are no more plaintext blocks remaining.

Decryption Take the first ciphertext block. Pass the ciphertext block and the key to the decryption function. XOR the result of the operation with the initialization vector (IV). The result is the first plaintext block. Pass the next ciphertext block and the key to the decryption function. XOR the result of the operation with the ciphertext block from the previous decryption step. The result is the next plaintext block. Go back to step 5 and repeat until there are no more ciphertext blocks remaining.

Error Propagation When there is a 1 bit error, only two blocks are impacted; one right after the other. Block with the error is badly impacted because the faulty ciphertext is processed with decryption function. Succeeding block has error in the position where the ciphertext had the original error because it is only impacted by the XOR process.

Properties message dependence limited error propagation no synchronization necessary can be used to provide data origin identification requires encryption AND decryption requires padding

Encryption and Decryption

Error Propagation