## Friday, October 15, 2021

### ECB Mode | Electronics Code Book Mode | Mode of Block Cipher | Application of ECB Mode

Introduction

Cryptographic algorithm works on main two techniques: block and stream ciphers.

In a stream cipher, the plaintext is encrypted one bit at a time. In a block cipher, the plaintext is broken into blocks of a fixed length and the bits in each block are encrypted together. One of the main issues with block ciphers is that they only allow you to encrypt messages the fixed size as their block length.

If plaintext, which has a block size 64 bits easily encrypt. But encrypt a 65-bit message, you need a way to define how the second block should be encrypted.

The solution to this is called block cipher modes of operation. Need of block cipher mode is basic building block for providing data security. In block cipher rather than encrypting one bit at a time, block of bits is encrypted at a time.

There are 5 modes of operation for block cipher that may be used in a wide variety of applications like symmetric key cryptographic algorithm. These modes define how data encrypted and decrypted.

Electronics Codebook Mode (ECB)

In ECB (Electronic Code Book) mode the given plain text message is divided into blocks of 64 bits each and each 64 bits blocks gets encrypted independently. The plaintext box produces cipher text of same size. All blocks of plaintext are encrypted using same key. Cipher text is decrypted using same key of encryption key.

Figure shows the encryption and decryption process of ECB mode.

 Figure: Encryption Process of ECB Mode

 Figure: Decryption Process of ECB Mode

The drawback of ECB mode is that for occurrence of more than one plaintext block in the input generates the same cipher text block in the output, which gives clue to the attacker.

For example, “ABC” plain text convert into 64-bit block and it generates 64-bit cipher text “XYZ”.

Application of ECB Mode

Only small messages can be encrypted to using ECB mode of operation.

Mostly ECB mode used, transmitting a single value in secure fashion. Ex. Password or key used for encryption.