17.1 Encryption & Digital Certificates
A Level · 3 questions found
What this topic covers
Section titled “What this topic covers”- Encryption: public/private key, plain text, cipher text, symmetric vs asymmetric cryptography
- Sending a private message and a verified message using public/private keys
- Quantum cryptography: purpose, benefits and drawbacks
- SSL/TLS: purpose, client-server use, appropriate situations
- Digital certificates: how acquired; how used to produce digital signatures
Past paper questions
Section titled “Past paper questions” Q7
7
(a) Describe what is meant by a digital certificate.
............................................................................................................................................. [3]
(b) Explain the role of a digital certificate in creating a digital signature.
............................................................................................................................................. [2]
Show mark scheme
7(a) [3 marks]
mark per point (
max 3
)
A digital certificate is an electronic/online document.
used to authenticate/prove the identity of a website/the online identity of an individual/organisation
typically issued by a CA
For example: it contains information identifying a website owner/individual and a public key
max 3
)
A digital certificate is an electronic/online document.
used to authenticate/prove the identity of a website/the online identity of an individual/organisation
typically issued by a CA
For example: it contains information identifying a website owner/individual and a public key
7(b) [2 marks]
mark per point (
max 2
)
The digital certificate
provides the public key
… that can be used to validate the private key associated with the organisation/website/digital signature
max 2
)
The digital certificate
provides the public key
… that can be used to validate the private key associated with the organisation/website/digital signature
Q4
4
Sheila has a customer called Fred. Fred wants to send Sheila a confidential document as part of a
transaction.
Explain how Fred uses asymmetric encryption to send his document securely.
.................................................................................................................................................... [4]
Show mark scheme
4 [4 marks]
mark per mark point (
Max 4
)
Sheila’s computer uses an algorithm to generate a matching pair of keys private and public
Sheila’s computer sends Fred’s computer Sheila’s public key // Fred‘s computer acquires Sheila’s public key
Fred’s computer encrypts the document/plain text using Sheila’s public key to create cipher text
Fred’s computer sends the
cipher text
to Sheila’s computer
The cipher text can only be decrypted using Sheila’s
private key // Sheila’s computer uses Sheila’s private key to decrypt the cipher text.
Max 4
)
Sheila’s computer uses an algorithm to generate a matching pair of keys private and public
Sheila’s computer sends Fred’s computer Sheila’s public key // Fred‘s computer acquires Sheila’s public key
Fred’s computer encrypts the document/plain text using Sheila’s public key to create cipher text
Fred’s computer sends the
cipher text
to Sheila’s computer
The cipher text can only be decrypted using Sheila’s
private key // Sheila’s computer uses Sheila’s private key to decrypt the cipher text.
Q7
7
(a) Describe what is meant by a digital certificate.
............................................................................................................................................. [3]
(b) Explain the role of a digital certificate in creating a digital signature.
............................................................................................................................................. [2]
,
,
Show mark scheme
7(a) [3 marks]
mark per point (
max 3
)
A digital certificate is an electronic/online document.
used to authenticate/prove the identity of a website/the online identity of an individual/organisation
typically issued by a CA
For example: it contains information identifying a website owner/individual and a public key
max 3
)
A digital certificate is an electronic/online document.
used to authenticate/prove the identity of a website/the online identity of an individual/organisation
typically issued by a CA
For example: it contains information identifying a website owner/individual and a public key
7(b) [2 marks]
mark per point (
max 2
)
The digital certificate
provides the public key
… that can be used to validate the private key associated with the organisation/website/digital signature
max 2
)
The digital certificate
provides the public key
… that can be used to validate the private key associated with the organisation/website/digital signature