Difference between Block Cipher and Stream Cipher

The computer is a machine. It cannot understand the English that we humans usually use. The computers can only understand and process in the binary codes, which consist of numbers that are 1 and 0. So, the computers take the input from the users in the English and that is converted into the cipher text using the techniques called Block cipher and stream cipher.

What is Block Cipher?

The Block cipher can be defined as a technique to produce the cipher text of equal length by treating a block of plain text. In this technique, normally a block of size 64 and 128 bits is used. The Block cipher techniques consider a block of code as whole or as a single text. This technique follows a procedure in which different number of blocks of text of different bits is used and with the help of symmetric key cipher, the cipher text is generated or produced. The plaintext in block cipher is divided into a block and it follows an order in encryption of data.

What is Stream Cipher?

The stream cipher can be defined as a technique to produce the cipher text from the plaintext of very small sizes. It is a technique that encrypts a digital data stream of the size one bit or one byte. It uses asymmetric Key cipher that it uses only one key for both encryption and decryption. The encryption in the stream cipher technique is done bit by bit.

Differences between Block Cipher and Stream Cipher

Block Cipher

• The block cipher technique uses 64 or more bits in the encryption process.
• The block cipher technique uses both confusion and diffusion techniques for the conversion of data into cipher text.
• The block cipher usually operates on large blocks of data. In which the plain text which contains sentences and the words in the sentence are considered as blocks.
• The block cipher is usually a slower process when compared with stream cipher because it usually operates on the larger blocks of data.
• To implement the block cipher technique, it requires more code.
• The block cipher technique has high diffusion value.
• In the block cipher technique, the reuse of key is possible.
• It provides integrity and authentication.
• It is more suitable for software implementation.

Stream Cipher

• The Stream cipher technique usually operates over the smaller units of play in text.
• The stream cipher technique is faster, and the time complexity is very less.
• The stream cipher technique does not provide both integrity and authentication unlike the block cipher provides.
• The stream cipher technique requires less code to implement the process.
• The diffusion value in the stream cipher technique is very low.
• The cipher key can only be used once and cannot be further reused in this process.
• It is more suitable for hardware implementation.

Advantages of Block Cipher

The block cipher technique got many advantages:

• It is easy to operate with the large blocks of data using this technique.
• The block cipher technique provides both integrity and authentication.
• The reusability of key is possible in the block cipher technique. This technique helps in securing the data.

Advantages of Stream Cipher

The stream cipher technique requires very less code. The stream cipher technique requires less time when compared to the block cipher technique. The stream cipher is easier because it uses XOR operations. This technique helps in securing the data.

Disadvantages of Block Cipher

The block cipher technique is slow when compared to stream cipher. The block cipher technique requires more code to make the process of making plain text into cipher text. It can only work over the large blocks of code.

Disadvantages of Stream Cipher

The stream cipher technique has the low diffusion value. The reusability of the cipher key is not possible in this technique. We should always create a new key every time when we take the new plain text.

Differences in tabular form

Block Cipher	Stream Cipher
The block cipher technique uses 64 or more bits in the encryption process.	The block cipher technique uses 8 bits in the encryption process.
The block cipher technique provides both integrity and authentication which makes it more efficient.	The stream cipher technique does not provide both integrity and authentication unlike the block cipher provide.
It is more suitable for s/w implementation.	It is more suitable for h/w implementation.
The block cipher technique has high diffusion value.	The diffusion value in the stream cipher technique is very low.
To implement the block cipher technique, it requires more code.	The stream cipher technique requires less code to implement the process.
In the block cipher technique, the reusability of key is possible.	The cipher key can only be used once and cannot be further reused in this process.
The block cipher is usually a slower process when compared with stream cipher.	The stream cipher technique is faster, and the time complexity is very less.