Question at position 13 Asymmetric encryption requires two keys: a public key and a private key. What is the main purpose of this approach?To ensure only the private key holder can decrypt the data To improve file compressionTo allow the same key for encryption and decryptionTo bypass passwordsClear my selection单项选择题
A
To ensure only the private key holder can decrypt the data
B
To improve file compression
C
To allow the same key for encryption and decryption
D
To bypass passwords

Question

Question at position 13 Asymmetric encryption requires two keys: a public key and a private key. What is the main purpose of this approach?To ensure only the private key holder can decrypt the data To improve file compressionTo allow the same key for encryption and decryptionTo bypass passwordsClear my selection单项选择题

A

To ensure only the private key holder can decrypt the data

B

To improve file compression

C

To allow the same key for encryption and decryption

D

To bypass passwords

BlackTom AI · Accepted Answer

Public-key (asymmetric) cryptography uses a pair of mathematically related keys: a public key for encrypting (or verifying) and a private key for decrypting (or signing).

1. Relevant knowledge points and concepts
- Asymmetric encryption: each user has a public key (widely distributed) and a private key (kept secret).
- Confidentiality: a message encrypted with a recipient’s public key can only be decrypted by that recipient’s private key.
- Contrast with symmetric encryption: a single shared secret key is used for both encryption and decryption.
- Digital signatures: the private key can sign data and anyone with the public key can verify the signature.

2. Step-by-step reasoning process
- Step 1: Alice obtains Bob’s public key (which is safe to share).
- Step 2: Alice encrypts her message using Bob’s public key, producing ciphertext C = E_pubB(M).
- Step 3: Alice sends C to Bob.
- Step 4: Only Bob, who holds the corresponding private key, computes M = D_privB(C) to recover the plaintext.
- Because only the private key complements the public key mathematically, no other party can feasibly decrypt C.

3. Calculations / intermediate steps
- Conceptual mapping: Encryption function E_pub and decryption function D_priv satisfy D_priv(E_pub(M)) = M for the matching key pair. (No numeric calculations are required here.)

4. Why the correct answer is correct
- The main purpose of asymmetric encryption is confidentiality and secure key distribution: ensuring that only the holder of the private key can decrypt data encrypted with the matching public key.

5. Why the other options are incorrect
- "To improve file compression": encryption is unrelated to compressing data; it typically makes data look random and can reduce compressibility.
- "To allow the same key for encryption and decryption": that describes symmetric encryption, not asymmetric.
- "To bypass passwords": asymmetric encryption is not a method to bypass authentication; it secures data and enables secure key exchange, but does not circumvent password mechanisms.

6. Conclusion
This explanation confirms the correct answer: To ensure only the private key holder can decrypt the data.

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