What is the Difference Between Confusion and Diffusion?

Confusion and diffusion are very important properties in cryptography that enhance the security of ciphers. Understanding the difference between diffusion and confusion is very handy when it comes to encryption. In this article, I will be discussing confusion vs diffusion and their roles in cryptography.

Before exploring the key differences between these two terms, I would like to explain the meaning and definition of each of them. So, what is confusion?

Confusion refers to making the correlation between the key and the ciphertext as complex and intricate as possible. This simply means confusion is used for creating clueless ciphertext.

For ciphertexts using confusion effectively, each bit of the ciphertext should depend on the entire key and various ways on different bits of the key. This means by changing one bit of the key should result in a huge change in the ciphertext. Now, what is diffusion?

Diffusion refers to the property that the redundancy in statistics of the plaintext is dissipated in the statistics of the ciphertext. This simply means diffusion is used for increasing the redundancy of the plaintext over a major part of the ciphertext to make it obscure.

For example, in diffusion, the non-uniformity in the distribution of the individual letters in the plaintext is redistributed into the non-uniformity in the distribution of much larger elements of the ciphertext, thus, making it hard to detect.

For ciphers that use diffusion effectively, if one bit of the plaintext is changed, then the ciphertext should change completely and unpredictably.

Difference between confusion and diffusion

  • Confusion is used to generate vague ciphertext whereas diffusion is used to generate obscure, plaintexts.
  • Confusion basically results in increased vagueness whereas diffusion result to increased redundancy.
  • Confusion is achieved by use of a substitution algorithm while diffusion is achieved by use of a transposition algorithm.
  • The main aim of confusion is to make the relationship between statistics of the ciphertext and the value of the encryption key as complicated as possible whereas diffusion seeks to make the statistical relationship between the plaintext and ciphertext as hard as possible.
  • Diffusion is only used in block ciphers whereas confusion is used in both stream and block ciphers.

Now I want to hear from you.

What do you think of confusion vs diffusion?

Or maybe I missed an important difference between confusion and diffusion.

Either way, let me know by leaving a comment below.


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