What are ECB and CBC encryption? (2024)

Cryptography methods such as Electronic Code Book (ECB) and Cipher Block Chaining (CBC) are widely used.

ECB is a simple method of encrypting plaintext by dividing it into fixed-size blocks and encrypting each block independently using the same secret key. In other words, if the same plaintext block appears more than once in the message, it will be encrypted into the same ciphertext block (aka will look the same). The ECB encryption method is relatively easy to implement; however, it can be vulnerable to certain types of attacks, such as pattern recognition.

By contrast, CBC is a more secure encryption method that addresses the weaknesses of ECB. CBC encrypts plaintext blocks using the same key and combines them with the previous ciphertext blocks through an operation called an XOR. Thus, even if the same plaintext block appears multiple times in the message, it will be encrypted to a different ciphertext block each time.

The major difference between ECB and CBC is that ECB encrypts each block independently, whereas CBC encrypts each block with the previous block. CBC is therefore considered more secure and resistant to pattern recognition attacks than ECB.

Implementation of CBC mode requires an initialization vector (IV), which is a random value added to the first plaintext block before encryption. An IV is sent along with an encrypted message, so the receiver can use it to decrypt it.

ECB and CBC are symmetric-key encryption methods, meaning that the same key is used for encryption and decryption. As computing power increases, it becomes increasingly important to use more secure encryption methods, such as AES-GCM or RSA-OAEP.