Cryptography & Information Security Flashcards

Which type of encryption uses the same key for both encryption and decryption?

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.

What is the key length used by AES-256?

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.

Which property of a cryptographic hash function ensures that two different inputs cannot produce the same hash output?

Answer: Collision resistance

Collision resistance means it is computationally infeasible to find two different inputs that produce the same hash output.

What distinguishes a hash function from encryption?

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.

What cryptographic concept ensures that a sender cannot later deny having sent a message?

Answer: Non-repudiation

Non-repudiation, typically achieved through digital signatures, prevents a sender from denying authorship of a message they signed.

Which cipher is theoretically unbreakable when used correctly because its key is as long as the message and used only once?

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.

What is steganography in the context of information security?

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.