Section A
Multiple Choice
Select the best answer for each question.
What is RSA named after?
In RSA, which component is shared between both the public key and the private key?
To encrypt a message for Bob using RSA, Alice should use:
To create a digital signature, the sender uses:
Why would a Certification Authority (CA) revoke a digital certificate?
Which best describes a Certification Authority (CA)?
The security of RSA is based on the computational difficulty of:
Which of the following provides non-repudiation?
In the first step of RSA key generation, what are p and q?
In PKI, which component stores certificates and Certificate Revocation Lists (CRLs) in a publicly accessible database?
Section B
True or False
Decide whether each statement is TRUE or FALSE.
Asymmetric key cryptography uses the same key for both encryption and decryption.
✅ True
❌ False
A digital signature provides non-repudiation, meaning the sender cannot deny having signed the message.
✅ True
❌ False
SHA-1 is currently the recommended hashing algorithm for security-critical applications because it produces a 512-bit digest.
✅ True
❌ False
The modulus n appears in both the RSA public key and the RSA private key.
✅ True
❌ False
A Message Authentication Code (MAC) provides non-repudiation because it proves exactly who sent the message.
✅ True
❌ False
Section C
Short Answer
Type your answer. Smart keyword detection will grade your response — no need to be word-perfect, but include the key concepts.
What is the main idea behind asymmetric-key cryptography? What mathematical concept does it rely on?
What is a Digital Certificate? Who creates it, and what problem does it solve?
What is a Certificate Revocation List (CRL) and how are revoked certificates identified within it?
Explain the difference between a hash function and a MAC (Message Authentication Code). What extra security does MAC provide?
Describe the role of the Registration Authority (RA) in a PKI system. How does it differ from the Certification Authority (CA)?
Section D
RSA Calculation
Work through RSA calculations step by step. Enter numerical answers.
Given p = 3 and q = 11, calculate n and φ(n).
p = 3, q = 11
n = p × q = ?
φ(n) = (p−1)(q−1) = ?
Using the RSA setup where p=3, q=11, e=7, d=3, n=33: encrypt the message M=2.
Encryption formula: C = M^e mod n
C = 2^7 mod 33 = ?
Using the same RSA setup (d=3, n=33), decrypt the ciphertext C=29.
Decryption formula: M = C^d mod n
M = 29^3 mod 33 = ?
Section E
Concept Application
Apply your knowledge to real-world scenarios.
Alice wants to send Bob a message that is both encrypted (confidential) AND digitally signed. Describe step by step which keys she uses and in what order.
Bob receives a digitally signed document from Alice. Explain how Bob verifies the signature and what it proves if the verification succeeds.
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