A network stream needs to be encrypted. Sara, the network administrator, has selected a cipher which will encrypt 8 bits at a time before sending the data across the network. Which of the following has Sara selected?
A block cipher encrypts data into fixed-length groups of bits, called a block. In this question, the cipher is transmitting the data one block at a time.
In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called blocks. They are specified elementary components in the design of many cryptographic protocols and are widely used to the encryption of large amounts of data, including data exchange protocols. It uses blocks as an unvarying transformation.
Even a secure block cipher is suitable for the encryption of only a single block of data at a time, using a fixed key. A multitude of modes of operation have been designed to allow their repeated use in a secure way to achieve the security goals of confidentiality and authenticity. However, block ciphers may also feature as building blocks in other cryptographic protocols, such as universal hash functions and pseudorandom number generators.