How Does Block Cipher Differs from Stream Cipher?

Stream Cipher

  • A stream cipher is an encryption algorithm that encrypts 1 bit or byte of plaintext at a time. It uses an infinite stream of pseudorandom bits as the key.
  • Examples of Stream Cipher
    One-time pad.
    Block Cipher in OFB OR CRT MODE. 
  • A stream cipher is synchronous if its key sequence does not depend on the plain- and ciphertexts but only on the previous elements of the key sequence and the initial key.

Block Cipher

  • Partition the text into relatively large (e.g. 128 bits) blocks and encode each block separately. The encoding of each block generally depends on at most one of the previous blocks.
    the same “key” is used at each block.
  • A block cipher is a method of encrypting text (to produce ciphertext) in which a cryptographic key and algorithm are applied to a block of data (for example, 64 contiguous bits) at once as a group rather than to one bit at a time. The main alternative method, used much less frequently, is called the stream cipher.