Block cipher modes of operation
Block ciphers can operate in different encryption modes, also known as modes of operation. As we already know, block ciphers encrypt plaintext data block by block. Encryption modes specify how blocks of ciphertext are chained together. We are now going to review most popular operation modes.
Reviewing the Electronic Code Book mode
The simplest operation mode is Electronic Code Book (ECB). In this mode, each plaintext block is encrypted into a ciphertext block using only the encryption key, without using an IV or previous plaintext or ciphertext blocks. Then, the ciphertext blocks produced are concatenated.
The ECB mode can be illustrated by the following image:
Figure 2.3 – How ECB mode works
Image Source: Wikipedia, licensing: Public Domain
In the ECB mode, the same plaintext always produces the same ciphertext. It is a security issue because patterns in the plaintext are preserved in the ciphertext and are...
