What is the Difference Between Stream Cipher and Block Cipher?

The main difference between stream ciphers and block ciphers lies in the way they process and encrypt data. Here are the key differences between the two:

1. Data processing: Block ciphers encrypt the plaintext in fixed-size blocks, while stream ciphers encrypt the plaintext bit by bit.
2. Speed: Stream ciphers are generally faster than block ciphers because they work on a more sequential manner, processing data bit by bit.
3. Resource requirements: Block ciphers require more processing power and memory because they process data in fixed-size blocks. In contrast, stream ciphers typically have lower memory requirements and need less processing power.
4. Key size: Block ciphers usually have longer keys to provide a higher level of security, while stream ciphers have smaller keys.
5. Encryption method: Block ciphers use both confusion and diffusion principles to encrypt data, while stream ciphers use only the confusion principle.
6. Algorithm modes: Block ciphers use modes like Electronic Code Book (ECB) and Cipher Block Chaining (CBC), while stream ciphers use modes like Cipher Feedback (CFB) and Output Feedback (OFB).
7. Applications: Block ciphers are used for data-at-rest encryption, while stream ciphers are used for data-in-transit encryption.

In summary, block ciphers are generally more secure and slower, while stream ciphers are faster but may be less secure. The choice between the two depends on the specific requirements and constraints of the encryption application.

Comparative Table: Stream Cipher vs Block Cipher

Here is a table comparing the differences between stream ciphers and block ciphers:

Key:

• Processing: Stream ciphers encrypt data bit-by-bit, while block ciphers encrypt data in fixed-size blocks.
• Key Size: Stream ciphers generally use smaller keys than block ciphers.
• Resource Use: Stream ciphers typically require fewer resources than block ciphers.
• Encryption Speed: Stream ciphers are generally faster than block ciphers.
• Modes: Stream ciphers use modes like CFB (Cipher Feedback) and OFB (Output Feedback), while block ciphers use modes like ECB (Electronic Codebook) and CBC (Cipher Block Chaining).
• Techniques: Stream ciphers work on substitution techniques, while block ciphers work on transposition techniques.
• Complexity: Stream ciphers are generally more complex than block ciphers.
• Confusion/Diffusion: Stream ciphers use confusion, while block ciphers use both confusion and diffusion.
• Reversibility: Reversing encrypted text is easier in stream ciphers than in block ciphers.