Difference between Block Cipher and Stream Cipher

Prerequisite – Block cipher modes of operation
Block Cipher and Stream Cipher belongs to the symmetric key cipher. These two block ciphers and stream cipher are the methods used for converting the plain text into ciphertext. 

The main difference between a Block cipher and a Stream cipher is that a block cipher converts the plain text into cipher text by taking plain text’s block at a time. While stream cipher Converts the plain text into cipher text by taking 1 byte of plain text at a time. 

Let’s see the difference between them:

S.NO	Block Cipher	Stream Cipher
1.	Block Cipher Converts the plain text into cipher text by taking plain text’s block at a time.	Stream Cipher Converts the plain text into cipher text by taking 1 byte of plain text at a time.
2.	Block cipher uses either 64 bits or more than 64 bits.	While stream cipher uses 8 bits.
3.	The complexity of block cipher is simple.	While stream cipher is more complex.
4.	Block cipher Uses confusion as well as diffusion.	While stream cipher uses only confusion.
5.	In block cipher, reverse encrypted text is hard.	While in-stream cipher, reverse encrypted text is easy.
6.	The algorithm modes which are used in block cipher are ECB (Electronic Code Book) and CBC (Cipher Block Chaining).	The algorithm modes which are used in stream cipher are CFB (Cipher Feedback) and OFB (Output Feedback).
7.	Block cipher works on transposition techniques like rail-fence technique, columnar transposition technique, etc.	While stream cipher works on substitution techniques like  Caesar cipher, polygram substitution cipher, etc.
8.	Block cipher is slow as compared to a stream cipher.	While stream cipher is fast in comparison to block cipher.
9.	Suitable for applications that require strong encryption, such as file storage and internet communications	Suitable for applications that require strong encryption, such as file storage and internet communications
10.	More secure than stream ciphers when the same key is used multiple times	Less secure than block ciphers when the same key is used multiple times
11.	key length is Typically 128 or 256 bits	key length is Typically 128 or 256 bits
12.	Operates on fixed-length blocks of data	Encrypts data one bit or byte at a time

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