# Can a Substitution Cipher achieve Confusion and Diffusion

Can a substitution cipher achieve confusion and diffusion?

By a substitution cipher I mean one where each character is replaced by another. By confusion my definition is that to solve the question, find key $$k$$ such that $$E_k(m) = c$$, should be difficult and diffusion is where non-uniformities in the message are distributed by the encryption function to make it more uniform.

So is it possible for a substitution cipher to achieve both? I believe it can't achieve diffusion since it treats each character independently but it may be able to achieve confusion (possibly the mono-alphabetic substitution cipher).

• The modern version of poly-alphabetic ciphers is the block ciphers. Commented Apr 26 at 7:38
• @kelalaka I understand that but my question was what does this basic mono-alphabetic substitution achieve. Does it achieve confusion and diffusion? Commented Apr 26 at 22:24
• I don't know what you are trying to achieve. Construct 8 char blocks, apply usual permutation then permute the positions then make this 16 round with different permutation in each round, done! Commented Apr 27 at 9:15
• @kelalaka This is just theoretical, I am learning about Shannon's diffusion and confusion and was wondering if this can be achieved by something as simple as a caesar cipher or mono-alphabetic cipher which only changes a plaintext char by char instead of something like a feistel structure you described. Commented Apr 27 at 10:55
• did you search for similar questions on this site? Commented Apr 27 at 13:55