SE Cryptography and PKI 1 — Questions and Answers
Question 1: Which type of encryption uses the same key for both encryption and decryption?
- Asymmetric encryption
- Symmetric encryption (Correct answer)
- Hashing
- Steganography
Correct answer: Symmetric encryption
Symmetric encryption (e.g., AES) uses a single shared secret key for both encrypting and decrypting data.
Question 2: What is the primary purpose of a Certificate Authority (CA) in a PKI?
- Generate passwords for users
- Issue and sign digital certificates to verify identity (Correct answer)
- Encrypt data in transit
- Manage firewall rules
Correct answer: Issue and sign digital certificates to verify identity
A CA is a trusted entity that issues, signs, and manages digital certificates that bind a public key to an identity.
Question 3: Which algorithm is widely used for asymmetric key exchange and digital signatures in TLS certificates?
- AES-256
- SHA-256
- RSA (Correct answer)
- HMAC
Correct answer: RSA
RSA is a widely deployed asymmetric algorithm used for digital signatures and key exchange in PKI and TLS.
Question 4: A digital signature provides which two security properties?
- Confidentiality and availability
- Authentication and non-repudiation (Correct answer)
- Integrity and confidentiality
- Authorization and accounting
Correct answer: Authentication and non-repudiation
Digital signatures verify the signer's identity (authentication) and prevent them from denying the action (non-repudiation).
Question 5: What is the difference between a hash function and encryption?
- Hashing is reversible; encryption is not
- Encryption is faster than hashing
- Hashing is a one-way function with no decryption; encryption is reversible with a key (Correct answer)
- Hashing uses public keys; encryption uses private keys
Correct answer: Hashing is a one-way function with no decryption; encryption is reversible with a key
Hash functions produce a fixed-length digest that cannot be reversed, while encryption transforms data that can be decrypted with the correct key.
Question 6: What is a Certificate Revocation List (CRL) used for?
- Listing all issued certificates
- Publishing certificates that have been revoked before their expiry (Correct answer)
- Renewing expired certificates
- Storing private keys
Correct answer: Publishing certificates that have been revoked before their expiry
A CRL is a list published by a CA of certificates that have been revoked and should no longer be trusted.
SE Cryptography and PKI 1
Which type of encryption uses the same key for both encryption and decryption?