CCP Cryptography & Information Security 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)
- Public-key encryption
- Hybrid encryption
Correct answer: Symmetric encryption
Symmetric encryption uses a single shared secret key for both encrypting and decrypting data, making it fast but requiring secure key distribution.
Question 2: What is the key length used by AES-256?
- 128 bits
- 192 bits
- 256 bits (Correct answer)
- 512 bits
Correct answer: 256 bits
AES-256 uses a 256-bit key, which is the longest standard key size for AES and provides the highest security level of the AES variants.
Question 3: Which property of a cryptographic hash function ensures that two different inputs cannot produce the same hash output?
- Preimage resistance
- Collision resistance (Correct answer)
- Avalanche effect
- Key diffusion
Correct answer: Collision resistance
Collision resistance means it is computationally infeasible to find two different inputs that produce the same hash output.
Question 4: What distinguishes a hash function from encryption?
- Hashing is faster than encryption
- Hashing is a one-way function with no decryption key (Correct answer)
- Hashing uses larger keys than encryption
- Hashing requires two parties to share a key
Correct answer: Hashing is a one-way function with no decryption key
Hashing is a one-way function designed to be irreversible; there is no key and the original data cannot be recovered from the hash.
Question 5: What cryptographic concept ensures that a sender cannot later deny having sent a message?
- Confidentiality
- Integrity
- Non-repudiation (Correct answer)
- Availability
Correct answer: Non-repudiation
Non-repudiation, typically achieved through digital signatures, prevents a sender from denying authorship of a message they signed.
Question 6: Which cipher is theoretically unbreakable when used correctly because its key is as long as the message and used only once?
- Vigenère cipher
- One-time pad (Correct answer)
- Caesar cipher
- Blowfish cipher
Correct answer: One-time pad
The one-time pad is provably unbreakable when the key is truly random, at least as long as the message, secret, and never reused.
Question 7: What is steganography in the context of information security?
- Encrypting data using a symmetric algorithm
- Hiding data within other non-secret data to conceal its existence (Correct answer)
- Converting data into an unreadable format using keys
- Compressing data to reduce transmission overhead
Correct answer: Hiding data within other non-secret data to conceal its existence
Steganography hides secret information within ordinary, non-secret files (such as images or audio) so that the existence of the hidden message is concealed.
CCP Cryptography & Information Security 1
Which type of encryption uses the same key for both encryption and decryption?