ECB vs CBC

Difference between ECB vs CBC

ECB and CBC are algorithm modes, both work on a block cipher. Block cipher is a technique that involves encryption of one block of text at a time, decryption also takes one block of encrypted text at a time. Algorithm mode is a combination of a series of the basic algorithm steps on block ciphers and some kind of feedback from previous steps. ECB stands for Electronic Code Book, while CBC stands for Cipher Block chaining. ECB is suitable for encryption small messages, while using CBC we can encrypt a large message. In this topic, we are going to learn about ECB vs CBC.

What is ECB?

ECB (Electronic Codebook) is the simplest mode of operation. In this algorithm mode, at the sender site, plain text messages are divided into sub-blocks each of 64 bits. Then each sub-block is encrypted independently. To encrypt all blocks the same key is used and generates the ciphertext. At the receiver side, the incoming ciphertext is divided into sub-blocks each of 64 bits, then the same key which is used for encryption is used for decrypting the ciphertext block and generating the corresponding plain text block. As the same key is used for encrypting all blocks, if the plain text block repeats in the original message, the corresponding ciphertext will also repeat. Hence the ECB is used for small messages.

What is CBC?

CBC (Cipher Block Chaining) mode works on block ciphers, it ensures that even if the block of plain text repeats, it will generate the different ciphertext for corresponding plain text blocks. To implement this, CBC uses a feedback mechanism. Plain text messages are divided into sub-blocks each of 64 bits, then the first block of plain text and IV are combined using XOR and then encrypted using a key to produce the ciphertext. Then the first block of ciphertext and the second block of plain text are combined using XOR and then encrypted using a key, the same is continued for all blocks. The same key is used for all blocks.

At the receiver side, the first block of ciphertext is decrypted using the same key used for encryption, then the result and IV are combined using XOR and generate the plain text block. The second ciphertext block is also decrypted using the same key and then the result is combined with the first block of the ciphertext using XOR and generates the second block of plain text. The same is continued for all blocks.

Head to Head Comparison between ECB vs CBC (Infographics)

Below are the top differences between ECB vs CBC.

Key Differences Between ECB and CBC

ECB stands for Electronic Code Book while CBC stands for Cipher Block Chaining
ECB is used for transmitting a single value whereas CBC mode is used for a block of text authentication
In ECB, each block of ciphertext that is encrypted is independent of other cipher blocks, whereas in CBC each block of ciphertext is dependent on corresponding current input plain text as well as a previous plain text block
ECB neither uses IV factor nor performed the XOR operations, whereas CBC uses both IV factor and XOR Operation.
Electronic code block does use a feedback mechanism whereas Cipher Block Chaining uses a feedback mechanism.
If the plain text block is repeated in an original message then ECB generates the same ciphertext block for the corresponding plain text block, whereas CBC generates different ciphertext blocks for the corresponding plain text block.
In ECB mode, the chances of decoding ciphertext is easier, hence it is used for encryption small message only, while in CBC mode, the chances of decoding ciphertext are quite tough, it can be used for encrypting large messages.

Comparison Table for ECB and CBC

Below is the comparison table which lists out the difference between the ECB and CBC.

Sr. No	ECB	CBC
1	ECB stands for Electronic Code Book	CBC stands for Cipher Block Chaining
2	It is used for the transmission of a single value in a secure manner	It is used for encrypting blocks of text authentication.
3	It is suitable for encrypting small messages	It is suitable for encrypting the large messages.
4	In ECB mode, it is easy to decode the ciphertext.	In CBC, it is quite difficult for the attacker to decode the ciphertext.
5	If the block of plain text is repeated in the original message, the corresponding ciphertext block will also repeat in the encrypted message	if the block of plain text is repeated in the original message, CBC will generate different ciphertext blocks for the repeated block of plain text.
6	ECB does not make use of the feedback mechanism	CBC makes use of a feedback mechanism.
7	In CBC, each block of ciphertext is independent of other blocks	In CBC, each block of ciphertext is dependent on the corresponding current input plain text block as well as the previous plain text block
8	ECB does not use IV (Initialization Vector)	CBC uses IV (Initialization Vector).
9	ECB does not perform XOR operation	CBC performs the XOR operation.