4. Modern Symmetric Ciphers
Computers internally represent printable data in binary format as strings of zeros and ones. Therefore any data are represented as a large block of zeros and ones. The processing speed of a computer is used to encrypt the block of zeros and ones. Securing all data in one go would not be practical, nor would it secure the data; hence the scheme was to treat data in chunks of blocks, which led to the concept of block ciphers.
Monoalphabetic Substitution Cipher
The most common value of a block is 64, 128, 256, or 512 bits. You will observe that these values ...