What is the first step when combining encryption with steganography?

The first step when combining encryption with steganography is to encrypt plaintext with a private key. This step is essential because it ensures that the original data remains confidential. By encrypting the plaintext, you convert it into ciphertext, which is a scrambled version of the data that cannot be understood without the decryption key.

Once the data is encrypted, you can then proceed to the steganography phase, where the ciphertext can be hidden within a media file, such as an image or audio file. This two-step process enhances the security of the information by not only concealing the existence of the data (through steganography) but also by making it unreadable to unauthorized users (through encryption).

The other options refer to processes that come after the initial encryption step. Hiding the ciphertext inside a media file, for instance, would occur after the data has been encrypted. Similarly, extracting and decrypting the ciphertext are steps that would follow once the intended recipient has located the hidden data. Finally, knowing the existence of the message presupposes that someone is already aware of the data, which is not the initial stage of integrating encryption with steganography. Therefore, the correct sequence of actions begins with encrypting the plaintext.