Analyze a public-key cryptography scenario and identify the correct key used to verify a digital signature.
Lab Environment
Scenario
Riley sent a secret message to Louis. Before sending the message, Riley digitally signed the message using his private key. Louis received the message, verified the digital signature using the corresponding key to ensure that the message was not tampered during transit.
Cryptographic Simulation
Digital Signature Flow
👤Riley🔑 Private Key
🔏 Signed Message
👤Louis🔓 Riley's Public Key
[SIGN] Riley signs message with private key
[SEND] Signed message transmitted to Louis
[VERIFY] Louis verifies signature using Riley's public key
🔐 Sender signs with private key · Receiver verifies with sender's public key
Challenge
Select the correct answer:
Which of the following keys did Louis use to verify the digital signature in the above scenario?
💡 In public-key cryptography, a digital signature created with a private key can only be verified by the corresponding public key of the same person.
Knowledge Base
Mini Lesson
1
Definition: A digital signature is a cryptographic mechanism that uses a key pair (private and public) to verify the authenticity and integrity of a message.
2
How it works: The sender signs the message with their own private key. The receiver then uses the sender's public key to verify the signature. If verification succeeds, the message has not been altered.
3
Why it matters: Digital signatures ensure message integrity, authentication, and non-repudiation — the sender cannot deny having sent the message.
4
Real-world example: Signing an email with a PGP/GPG key so the recipient can verify it was truly sent by you and was not modified in transit.
5
Key takeaway: Sign with your private key, verify with the sender's public key. The key pair always belongs to the signer.