# When confusion is applied during encryption?

I know confusion is used in cryptography to make it more difficult to identify any relationship between the ciphertext and the symmetric key. I want to know when the confusion is applied during encryption, for example:

1. Confusion applied on the symmetric key K1 to form the modified symmetric key K2, and then K2 is used in the encryption: enc(Plain_text,K2).
2. K1 is used in encryption: Cipher_text = enc(Plain_text,K1), and then a confusion function is applied on Cipher_text.

Is it one of these two methods, or something else? An example would be appreciated.

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