D334 Introduction to Cryptography - Set 1 - Part 1

Correct Answer: It is considered unbreakable

A one-time pad is considered unbreakable because it uses a random key that is as long as the message and is used only once. This ensures that there is no repeating pattern that can be exploited by attackers.

Correct Answer: To manage cryptographic keys

An HSM is a tamper-resistant device designed to manage, store, and protect cryptographic keys and perform cryptographic operations.

Correct Answer: Cipher Block Chaining (CBC)

CBC mode XORs each plaintext block with the previous ciphertext block before encryption, ensuring that no two identical plaintext blocks produce the same ciphertext.

Correct Answer: Frequency analysis

Frequency analysis involves studying the frequency of letters or groups of letters in a ciphertext to break the encryption. It is particularly effective against simple substitution ciphers.

Correct Answer: It encrypts identical plaintext blocks into identical ciphertext blocks

ECB mode is insecure because it produces the same ciphertext for identical plaintext blocks, making it vulnerable to pattern analysis.

Correct Answer: SPECK

SPECK is a light-weight block cipher designed by the NSA, optimized for performance in hardware implementations, making it suitable for constrained environments like IoT devices.

Correct Answer: SHA-1

SHA-1 produces a 160-bit hash value, though it is now considered insecure and has been largely replaced by stronger algorithms like SHA-256 and SHA-512.

Correct Answer: RSA

RSA relies on the difficulty of factoring large prime numbers, which makes it secure for encryption and digital signatures, though it is computationally intensive.

Correct Answer: To provide a public key to verify signatures

A digital certificate binds a public key to an entity, allowing others to verify that entity’s signature or to encrypt messages using the public key.

Correct Answer: Public keys

In the Diffie-Hellman key exchange, the two parties exchange public keys, which are used along with their own private keys to derive a shared secret key.

Correct Answer: Homomorphic encryption

Homomorphic encryption allows mathematical operations to be performed on encrypted data without needing to decrypt it, ensuring data privacy during processing.

Correct Answer: Output Feedback (OFB)

OFB mode transforms a block cipher into a stream cipher by generating keystream blocks that are XORed with the plaintext, allowing block-by-block encryption.

Correct Answer: SHA-1

SHA-1 has been proven vulnerable to collision attacks, where two different inputs produce the same hash value, compromising the integrity of the hash.

Correct Answer: It uses smaller keys for the same level of security

ECC offers the same level of security as RSA but with much smaller key sizes, making it faster and more efficient, especially in resource-constrained environments.

Correct Answer: The attacker intercepts and alters communication between two parties

A MITM attack involves the attacker secretly intercepting and potentially altering communication between two parties, without them knowing.

Correct Answer: AES

AES is widely used in modern operating systems like Windows and macOS to encrypt individual files and entire disk volumes due to its strength and efficiency.

Correct Answer: The recipient's private key

In asymmetric encryption, a message encrypted with the recipient’s public key can only be decrypted by the recipient’s private key, ensuring confidentiality.

Correct Answer: To prevent replay attacks

A nonce is a number used once to ensure that old communications cannot be replayed by attackers, adding randomness to cryptographic protocols.

Correct Answer: RSA

RSA supports certain types of homomorphic encryption, allowing mathematical operations to be performed on ciphertext without decrypting it first.

Correct Answer: 128 bits

AES uses a fixed block size of 128 bits, regardless of the key size, which can be 128, 192, or 256 bits.