Cisco Cyber Security Practice Exam

What is the correct key to decrypt a symmetric encryption message sent by Jane to Raj?

1. Raj's public key

2. Raj's private key

3. Jane's public key

4. Jane's private key

The correct answer is: Raj's private key

In symmetric encryption, the same key is used for both encryption and decryption. This means that the key needed to decrypt a message is the same key that was used to encrypt it. Since the question specifies that Jane sent a symmetric encryption message to Raj, it implies that both Jane and Raj must have a shared secret key that was used during the encryption process. The option specifying Raj's private key is usually relevant in the context of asymmetric encryption, where public and private keys are used. In this scenario, referencing Raj's private key suggests that he has control over a secret associated with a public key, which isn't applicable in symmetric encryption. Therefore, understanding that the shared secret key (often implicitly understood in symmetric systems rather than expressed) is necessary illustrates that the key used for decryption must match what Jane used for encryption. In practice, if Raj were to decrypt messages from Jane, they would share a specific symmetric key beforehand, enhancing secure communication without the contextual references to public and private keys used in asymmetric systems.