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Table of contents
1.
Introduction
2.
Stream Cipher
3.
Block Cipher
4.
Difference between Stream Cipher and Block Cipher
5.
Frequently Asked Questions
5.1.
What is the Block Cipher method? 
5.2.
What is the difference between Cipher Feedback Mode and the Output Feedback Mode? 
5.3.
What is the difference between Electronic Code Block and Cipher Code Training? 
6.
Conclusion
Last Updated: Mar 27, 2024

How are Block Ciphers different from Stream Ciphers?

Author Neha Chauhan
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Introduction

Cryptography is the technique of securing the communication and exchange of information by converting plain text messages (human-readable text) into encrypted messages that are not in human-understandable format unless they apply a key to decrypt the message.

The algorithm used for encryption and decryption is called Cipher. 

Stream cipher and Block cipher are two of the many algorithms used in cryptography.

How is Block Cipher different from Stream Ciphers?


In this article, we will discuss the differences between Stream Cipher and Block Cipher. 

Stream Cipher

A Stream Cipher is an encryption algorithm that is applied to each of the bytes of the plain text. 

In this technique, a pseudorandom keystream of a size equal to the size of the plain text is created, which is then, XORed with the plain text to generate the cipher text. The pseudorandom keystream must be unique and should not be used more than once to secure the encryption. 

Advantages - Stream Ciphers are very easy to implement. They are very fast also, as the data will be sent bit by bit instead of waiting for the entire message to be ciphered. 

Disadvantages - We cannot use the same key more than once, as that will make it less secure. 

To learn more about Stream Ciphers, we recommend you read our article on stream Ciphers.

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Block Cipher

A Block Cipher is an encryption technique applied to a block of plain text i.e., the text is divided into blocks of equal length, and then the encryption key is applied to it. The size of the block is usually smaller than the size of the plain text; hence the plain text is divided into several smaller blocks. 

It uses a symmetric key i.e., the same key is used for encryption and decryption. 

There are five modes of Block Cipher - Electronic Code Book (ECB) Mode, Cipher Block Chaining (CBC) Mode, Cipher Feedback (CFB) Mode, Output Feedback (OFB) Mode and Counter (CTR) Mode. Each of these uses different types of encryption keys. 

To read more about modes of Block cipher, read this article.

Difference between Stream Cipher and Block Cipher

 

Stream Cipher

Block Cipher

Definition

Stream Cipher is an encryption technique in which the encryption key is applied bit by bit on the plain text.  Block Cipher is an encryption technique in which the encryption key is applied to a block of plain text. 

Bits Conversion

Only 8 bits can be transformed.  64 bits can be transformed at a time. 

Decrypting

Converting cipher text back to plain text is easy.  A combination of more bits gets involved, so the conversion of cipher text back to plain text is complex.

Principles

It works on the confusion principle. It uses both the confusion and diffusion principle. 

Algorithm

It uses Cipher Feedback and Output Feedback algorithms. It uses Electronic code block and Cipher Block Chaining algorithms.  

Technique

It uses substitution techniques. It uses transposition techniques. 

Source of Code

It requires less code. It requires more code. 

Frequently Asked Questions

What is the Block Cipher method? 

The Block cipher method is an encryption and decryption technique, in which the plain text is encrypted by dividing the text into blocks of equal size, producing blocks of cryptic text of the same size as the plain text. 

What is the difference between Cipher Feedback Mode and the Output Feedback Mode? 

The Cipher Feedback Mode and the Output Feedback Mode are very similar but there are two differences between them - the first difference is that in Output Feedback Mode, the encrypted text is given as input to the next phase unlike the cipher text in the Cipher Feedback Mode and the second difference is that the encrypted message is NOT divided into any parts in case of Output Feedback Mode. 

What is the difference between Electronic Code Block and Cipher Code Training? 

In the case of an Electronic Code Block, the phase is independent of each other while in Cipher Code Training the output cipher text of the previous block is given as an input for the XOR operation with the plain text.  

Conclusion

Pat yourself on the back for finishing this article. In this article, we discussed the differences between Stream Ciphers and Block Ciphers. 

Do not stop learning! We recommend you read these articles - 

🔥 What is Cryptography?

🔥 What are basic Cryptography tools?

🔥 Message Authentication Codes in Cryptography

🔥 Security in Cryptography

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