Cryptography Questions Medium
Cipher Block Chaining with Propagating Cipher Block Chaining (CBC-PCBC) is a mode of operation used in block ciphers for encryption and decryption. It is an extension of the CBC mode and provides additional security by introducing a feedback mechanism.
In CBC-PCBC mode, each plaintext block is XORed with the previous ciphertext block before being encrypted. This XOR operation adds diffusion and makes the encryption process more secure. Additionally, the result of this XOR operation is then XORed with the current plaintext block before encryption. This feedback mechanism propagates the changes made in the previous block to the current block, further enhancing the security.
The CBC-PCBC mode also requires an initialization vector (IV) to be used in the first block encryption. The IV is XORed with the plaintext block before encryption, providing randomness and preventing patterns from emerging in the ciphertext.
During decryption, the same process is followed in reverse. Each ciphertext block is decrypted and then XORed with the previous ciphertext block to obtain the plaintext block. The result is then XORed with the previous ciphertext block to retrieve the original plaintext.
Overall, CBC-PCBC mode provides improved security compared to the basic CBC mode by introducing the feedback mechanism and XOR operations. It helps prevent patterns and correlations from being exploited by attackers, making it a widely used mode of operation in cryptographic systems.