Block Cipher Vs Stream Cipher

Block Cipher and Stream Cipher are the methods used for converting the plain text into cipher text directly and belong to the family of symmetric key ciphers.

 The major difference between a block cipher and a stream cipher is that the block cipher encrypts and decrypts a block of the text at a time. On the other hand, stream cipher encrypts and decrypts the text by taking the one byte of the text at a time.

Key Differences Between Block Cipher and Stream Cipher

  1. Block cipher technique involves encryption of one block of text at a time, i.e. singly. Similarly, decrypt the text by taking one block after another. In contrast, Stream cipher technique involves encryption and decryption of one byte of the text at a time.
  2. Block cipher uses both confusion and diffusion while stream cipher relies only on confusion.
  3. The usual size of the block could be 64 or 128 bits in the Block cipher. As against, 1 byte (8 bits) at a time is converted in the stream cipher.
  4. Block cipher uses ECB (Electronic Code Book) and CBC (Cipher Block Chaining) algorithm modes. On the contrary, Stream cipher uses CFB (Cipher Feedback) and OFB (Output Feedback)algorithm modes.
  5. Stream cipher uses XOR function for converting the plain text into cipher text, that is the reason why it is easy to reverse the XORed bits. Whereas Block cipher does not use XOR for doing so.
  6. Block cipher uses the same key to encrypt each block while stream cipher uses a different key for each byte.

Conclusion:

Block Cipher and Stream Cipher differ in the way in which plain text is encrypted and decrypted. The idea behind block cipher is to divide the plain text into blocks further encrypt those blocks. While stream cipher converts plain text bit by bit similar to stream.

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