D334 Introduction to Cryptography - Set 4 - Part 1

Correct Answer: Preventing the sender from denying they sent a message

Non-repudiation ensures that the sender of a message cannot deny having sent it, typically achieved using digital signatures.

Correct Answer: It is used for encryption and can be freely distributed

In asymmetric encryption, the public key is used for encryption and can be freely distributed, while the private key is kept secret and used for decryption.

Correct Answer: ECC requires smaller key sizes for equivalent security

ECC provides the same level of security as RSA but with much smaller key sizes, making it more efficient in terms of storage and computation.

Correct Answer: To provide authentication and public key verification

A digital certificate is used to verify the identity of an entity and associate it with a public key for secure communications.

Correct Answer: Diffie-Hellman

Diffie-Hellman provides forward secrecy by ensuring that session keys are not derived from long-term keys, preventing compromise of past sessions.

Correct Answer: CTR

Counter (CTR) mode allows for parallel processing of blocks because each block is encrypted independently, improving encryption performance.

Correct Answer: An attacker intercepts and reuses valid data transmissions

A replay attack involves capturing and reusing legitimate data transmissions, often to gain unauthorized access or deceive systems.

Correct Answer: 128 bits

AES-128 uses a 128-bit key for encryption, providing a balance between security and performance.

Correct Answer: Side-channel attack

In a side-channel attack, the attacker analyzes the time, power consumption, or other physical characteristics of encryption operations to gather information about the encryption key.

Correct Answer: Diffie-Hellman

Diffie-Hellman is a key exchange protocol that allows two parties to securely exchange cryptographic keys over an untrusted network.

Correct Answer: To ensure data integrity

Hashing in digital signatures ensures that the data has not been altered by creating a unique hash of the data, which is signed by the sender for verification by the recipient.

Correct Answer: A substitution cipher that shifts letters by a fixed number

The Caesar cipher is a simple substitution cipher that shifts each letter of the plaintext by a fixed number of positions in the alphabet.

Correct Answer: It uses smaller key sizes, requiring less computational power

ECC uses smaller key sizes compared to RSA, making it more efficient for mobile devices with limited computational power.

Correct Answer: The attacker chooses plaintext to encrypt and observe the resulting ciphertext

In a chosen-plaintext attack, the attacker selects plaintext to encrypt and uses the resulting ciphertext to gather information about the encryption algorithm.

Correct Answer: CBC

Cipher Block Chaining (CBC) mode ensures that each ciphertext block depends on the encryption of the previous block, making it more secure than ECB.

Correct Answer: To ensure that identical plaintexts produce different ciphertexts

A nonce is a random value used only once in encryption to ensure that the same plaintext encrypted multiple times results in different ciphertexts.

Correct Answer: It is used for encryption and can be freely distributed

In asymmetric encryption, the public key is used for encryption and can be freely distributed, while the private key is kept secret for decryption.

Correct Answer: RSA

RSA is commonly used for digital signatures because it provides authentication and data integrity by allowing the recipient to verify the identity of the sender.

Correct Answer: To ensure that the same password generates different hash values

Salting adds random data to passwords before hashing to ensure that identical passwords result in different hash values, preventing attackers from using precomputed tables to crack hashes.

Correct Answer: AES

AES is used to secure Wi-Fi networks under WPA2, providing strong encryption to protect wireless communications.