RC4 is notable for having what kind of key usage?

RC4 is notable for having what kind of key usage?

• A. Variable key-size
• B. Fixed key-size
• C. Public-key
• D. No keys

Answer: (A)

RC4 uses a secret key to initialize its internal state and produce a keystream that is XORed with the plaintext. A key feature of RC4 is that its key length can vary; it supports keys from very short up to quite long, specifically from 1 to 256 bytes (8 to 2048 bits). This flexibility means the cipher doesn’t have a single fixed key size, but rather can operate with different key lengths depending on the needs of the implementation and the desired level of security. That’s why the correct description is that RC4 has variable key-size. It’s not a fixed key-size algorithm, which would imply only one key length is used. It’s also not public-key cryptography, which relies on asymmetric keys (a public and a private key). And it cannot be used without any key at all, since encryption with RC4 requires a secret key to generate the keystream.

RC4 uses a secret key to initialize its internal state and produce a keystream that is XORed with the plaintext. A key feature of RC4 is that its key length can vary; it supports keys from very short up to quite long, specifically from 1 to 256 bytes (8 to 2048 bits). This flexibility means the cipher doesn’t have a single fixed key size, but rather can operate with different key lengths depending on the needs of the implementation and the desired level of security. That’s why the correct description is that RC4 has variable key-size.

It’s not a fixed key-size algorithm, which would imply only one key length is used. It’s also not public-key cryptography, which relies on asymmetric keys (a public and a private key). And it cannot be used without any key at all, since encryption with RC4 requires a secret key to generate the keystream.