Public Key Infrastructure & Digital Certificates

Question 1

What is Public Key Infrastructure (PKI)?

Answer 1

Stores public keys and is trusted by all parties in a network or organization.

Question 2

How does an employee use PKI to send a secure email?

Answer 2

Employee A retrieves Employee B’s public key from the PKI, encrypts the email with B’s public key, and B decrypts it using their private key.

Question 3

What is the difference between a public key and a private key?

Answer 3

Public Key: Shared openly.
Private Key: Kept secret, used for decryption.

Question 4

What is the process for creating a digital signature?

Answer 4

Document content is hashed, and the hash is encrypted with the sender’s private key.

Question 5

How does a recipient verify a digital signature?

Answer 5

The recipient decrypts the hash using the sender’s public key and compares it with a newly hashed document.

Question 6

What does signing and verification refer to in digital signatures?

Answer 6

Signing = Sender’s private key
Verification = Sender’s public key

Question 7

What is a digital certificate?

Answer 7

A digital document issued by a Certificate Authority (CA) that binds a public key to an entity.

Question 8

How does a business use digital certificates?

Answer 8

A business signs a certificate with its private key, and a customer verifies it using the business’s public key.

Question 9

What happens in a combined email scenario involving encryption and digital signatures?

Answer 9

Employee A sends an encrypted and signed email to Employee B, encrypting it with B’s public key and signing it with A’s private key.

Question 10

What is the email handling process for an encrypted and signed email?

Answer 10

Verify the digital signature and decrypt the email content.

Question 11

What must the receiver know before encryption?

Answer 11

The receiver must know the cryptographic algorithm and the cryptographic key.

The key + algorithm = needed to decrypt!

Question 12

What is the goal when sending a secret key?

Answer 12

The goal is to send the secret key from A to B securely without coworkers seeing it.

Encrypt with B’s public key; only B’s private key can decrypt it.

Question 13

How should a secret key be sent?

Answer 13

Use the receiver’s public key to send a secret.

Only B’s private key can decrypt it.