Which of the following is used to add extra complexity before using a one-way data transformation algorithm?

Salting is the process of adding a unique, random string of data (the "salt") to a password before hashing it. This makes it more difficult for attackers to use precomputed rainbow tables or dictionary attacks, as each salted hash is unique, even for identical passwords. Key stretching, while also enhancing security, involves repeatedly applying a cryptographic hash function to a password to increase the time it takes to brute-force. Data masking obscures sensitive data but doesn't add complexity to a cryptographic algorithm. Steganography is the art of concealing a message within another message or a file, not directly related to enhancing cryptographic complexity.