How does an asymmetric key work?

How does an asymmetric key work?

• A. Public key can be freely distributed since it's only used to lock the data; private key decrypts
• B. Private key encrypts; public key decrypts
• C. Both keys are identical and interchangeable
• D. Symmetric key is used to secure the session only

Answer: (A)

The idea being tested here is how public-key cryptography uses two keys: a public key that can be shared openly to encrypt data, and a private key that is kept secret to decrypt it. When someone wants to send a confidential message, they encrypt it with the recipient’s public key. Only the recipient, who holds the private key, can decrypt the message. This separation allows anyone to send encrypted data to the recipient without needing a secret key to start with, while guaranteeing that only the intended recipient can read it. That’s why the statement that the public key can be freely distributed since it’s only used to lock the data and the private key decrypts is the best description of how asymmetric encryption preserves confidentiality. It captures the core function: public keys are public for encryption, private keys remain private for decryption. A note on the others: using the private key to encrypt and the public key to decrypt describes a different use—digital signatures, which verify origin and integrity rather than provide confidentiality. The idea that both keys are identical and interchangeable isn’t how asymmetric pairs work, since the two keys are related but distinct and have different roles. And mentioning a symmetric key is outside the basic mechanism described here; symmetric keys are used in a different type of cryptography, typically for securing the actual data after a secure channel is established, but not the described public-key encryption flow.

The idea being tested here is how public-key cryptography uses two keys: a public key that can be shared openly to encrypt data, and a private key that is kept secret to decrypt it. When someone wants to send a confidential message, they encrypt it with the recipient’s public key. Only the recipient, who holds the private key, can decrypt the message. This separation allows anyone to send encrypted data to the recipient without needing a secret key to start with, while guaranteeing that only the intended recipient can read it.

That’s why the statement that the public key can be freely distributed since it’s only used to lock the data and the private key decrypts is the best description of how asymmetric encryption preserves confidentiality. It captures the core function: public keys are public for encryption, private keys remain private for decryption.

A note on the others: using the private key to encrypt and the public key to decrypt describes a different use—digital signatures, which verify origin and integrity rather than provide confidentiality. The idea that both keys are identical and interchangeable isn’t how asymmetric pairs work, since the two keys are related but distinct and have different roles. And mentioning a symmetric key is outside the basic mechanism described here; symmetric keys are used in a different type of cryptography, typically for securing the actual data after a secure channel is established, but not the described public-key encryption flow.