What is Block Cipher in information security?

A block cipher is a set of encryption where plain text is first breaked into several blocks, each with a fixed size. Essentially, each block has the similar number of data bits. At any given time, the encryption procedure work on an individual block of plain text and uses the encryption key to transfer it into a block of ciphertext.

Each block is of the similar size (such as 64 bits). For example, a 160-bit plain text is encoded into 2 blocks of 64-bits each, while the third block will have the remaining balance of 32 bits. It will be padded with an extra 32 bits to support the similar size as other blocks.

A block cipher is an encryption approach that uses a deterministic algorithm forward with a symmetric key to encode a block of text, instead of encoding one bit at a time as in stream ciphers.

Block ciphers are pseudorandom permutation (PRP) classification that work on the fixed size block of bits. PRPs are functions that cannot be understand from absolutely random permutations and therefore, are treated reliable, until proven not true.

A block cipher works on a plaintext block of n bits to create a cipher text block of n bits. There are possible several plaintext blocks and, for the encryption to be changeable (i.e., for decryption to be possible), each should create a unique cipher text block. Such transformation is known as reversible, or non-singular.

Block cipher modes of operation have been produced to remove the chance of encrypting identical blocks of text the similar method, the ciphertext formed from the previous encrypted block is used to the next block.

A block of bits known as initialization vector (IV). It can be also used by modes of operation to provide ciphertexts remain definite even when the similar plaintext message is encrypted a number of times. A block cipher is a class of cipher that encrypts text by functioning blocks of the text through an algorithm that assortment it up. This is against a stream cipher that encrypts text one bit at a time.

For example, a block cipher would operate by encrypting the first paragraph of this lesson before changing on to the next paragraph.

A block cipher can repeat this phase until the whole lesson was encrypted. A stream cipher can start by encrypting the first character of the first paragraph before changing on the next character in the similar paragraph.

This procedure is repeated until the whole lesson is encrypted. Text that has been encrypted by a cipher is known as ciphertext. It can return the ciphertext back to its original state, it should be run through the cipher once again.