Question

A user is using an encryption system where a pair of keys is generated. One key is shared publicly, while the other key is kept secret by the owner and is used to decrypt messages or create digital signatures. Which key is being described?

• A. Public Key
• B. Session key
• C. Private key
• D. Shared key

Hint:

In Asymmetric Encryption: You Encrypt with the Public Key and Decrypt with the Private Key. In Digital Signatures: You Sign with the Private Key and Verify with the Public Key.

Answer 1

The Correct Option is C

Concept:
The question describes Asymmetric Cryptography, also known as Public Key Cryptography. Unlike symmetric systems that use one shared key, asymmetric systems use a mathematically related pair of keys: a Public Key and a Private Key.

Step 1: Analyzing the Key Pair.
In this system:
• Public Key: Can be distributed freely to anyone. It is used by others to encrypt a message intended for the owner or to verify the owner's digital signature.
• Private Key: Must be kept absolutely secret by the owner. It is used by the owner to decrypt incoming messages or to create a digital signature.

Step 2: Identifying the specific key in the prompt.
The prompt asks to identify the key that is:
• Kept secret by the owner.
• Used to decrypt messages.
• Used to create digital signatures. These three characteristics define the Private Key.

Step 3: Importance of the Private Key.
The security of the entire asymmetric system rests on the owner's ability to keep the private key secret. If the private key is compromised, any person who possesses it can read the owner's confidential mail and impersonate them by forging their digital signature.