The RSA encryption algorithm also works in reverse, that is, you can encrypt a…
2019
The RSA encryption algorithm also works in reverse, that is, you can encrypt a message with the private key and decrypt it using the public key. This property is used in
- A.
instruction detection systems
- B.
digital signatures
- C.
data compression
- D.
certification
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Correct answer: B
Answer: digital signatures
Why: RSA's ability to 'encrypt' with the private key and 'decrypt' with the public key is exactly how digital signatures are created and verified.
Step 1: Compute a cryptographic hash of the message (for example SHA-256).
Step 2: The signer encrypts (signs) that hash using their private key. The resulting value is the digital signature.
Step 3: A verifier decrypts the signature using the signer's public key to recover the hash, computes the hash of the received message, and compares the two hashes. A match verifies authenticity and integrity.
Benefits: digital signatures provide authentication (proves who signed), integrity (message unchanged), and non-repudiation (signer cannot deny the signature).
Note: While certification processes use digital signatures (for example, certificate authorities sign certificates), the direct application of encrypting with the private key is signing, so digital signatures is the most accurate answer.
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