What is the difference between cfb and cfb1 and cfb8 ? ( like openssl's aria-128-cfb & aria-128-cfb1 & aria-128-cfb8 )

What is the difference between cfb and cfb1 and cfb8 ? like openssl's aria-128-cfb and aria-128-cfb1 and aria-128-cfb8

edit: interestingly enough, there's also references to a cfb128 (example)

(title says it all but CSE won't let me post a question without a message body)

What is the difference between cfb and cfb1 and cfb8?

Well, first of all, we need examine what CFB is. Here is what the encryption process is:

• Take the previous $$n$$ bits of ciphertext (where $$n$$ is the block size of the cipher, for Aria, $$n=128$$

• Send it through the block cipher in encryption mode

• Extract $$k$$ bits of the result, exclusive-or that with the next $$k$$ bits of block text, and make that the next $$k$$ bits of ciphertext.

That's it. Each iteration of the loop encrypts $$k$$ bits of plaintext, generating $$k$$ bits of ciphertext, and performs one block cipher operation.

• For cfb1, $$k=1$$
• For cfb8, $$k=8$$
• For cfb, $$k=n$$ (or 128 for Aria)