Digital signatures and certificates in Computer Networks - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a digital signature?

A digital signature is a special code attached to a message or document that proves it came from a specific person and has not been changed.

beginner

What role does a certificate authority (CA) play in digital certificates?

A certificate authority is a trusted organization that issues digital certificates to verify the identity of people or websites.

intermediate

How does a digital signature help ensure message integrity?

It uses a unique code created from the message content that changes if the message is altered, so any change can be detected.

intermediate

What information is typically included in a digital certificate?

It usually contains the owner’s name, public key, expiration date, and the certificate authority’s digital signature.

beginner

Why are digital certificates important for secure websites?

They prove the website’s identity to users, helping prevent fake sites and enabling encrypted communication.

What does a digital signature primarily verify?

A The message length

B The sender's IP address

C The sender's identity and message integrity

D The message format

A digital signature confirms who sent the message and that it has not been changed.

Who issues digital certificates?

A Internet Service Providers

B Certificate Authorities

C Web Browsers

D Email Providers

Certificate Authorities are trusted organizations that issue digital certificates.

Which key is included in a digital certificate?

A Private key

B Symmetric key

C Session key

D Public key

Digital certificates include the public key to allow others to encrypt messages or verify signatures.

What happens if a message is changed after being digitally signed?

A The signature becomes invalid

B The message is encrypted again

C The message is deleted

D The signature remains valid

Any change to the message invalidates the digital signature, showing tampering.

Why do browsers show a padlock icon for some websites?

A The website uses a digital certificate

B The website is free

C The website has many visitors

D The website is new

The padlock means the website has a valid digital certificate and secure connection.

Explain in your own words what a digital signature is and why it is important.

Think about how you can trust a letter or email is really from someone and unchanged.

Describe the purpose of a digital certificate and the role of a certificate authority.

Consider how websites prove they are safe to visit.