D334 Introduction to Cryptography - Set 1 - Part 2

Correct Answer: RC4

RC4 is a stream cipher that was widely used in WPA and WEP encryption, though it has been deprecated in favor of more secure algorithms like AES-CCMP.

Correct Answer: RSA

RSA is an asymmetric encryption algorithm that uses a public/private key pair, unlike AES and DES, which are symmetric algorithms.

Correct Answer: Digital signature

A digital signature is used to verify the integrity of a message, ensuring it has not been altered during transmission and verifying the senders identity.

Correct Answer: Compromised long-term keys will not compromise past session keys

Perfect forward secrecy ensures that even if long-term keys are compromised, past session keys remain secure, as each session key is unique.

Correct Answer: Vulnerability to brute-force attacks

Password-based encryption is susceptible to brute-force attacks, where attackers try many possible passwords until they find the correct one.

Correct Answer: Cipher Block Chaining (CBC)

CBC mode uses an IV for the first block and XORs each subsequent block of plaintext with the previous ciphertext block, ensuring that identical plaintext blocks produce different ciphertexts.

Correct Answer: To return the remainder of a division

The modulus operator returns the remainder after dividing one number by another, and it is frequently used in cryptographic algorithms like RSA and Diffie-Hellman.

Correct Answer: Ciphertext-only attack

A ciphertext-only attack relies on the ability to analyze multiple ciphertexts encrypted with the same key to deduce the key or plaintext, often using statistical methods.

Correct Answer: By shifting the plaintext letters by a fixed number of positions

In a Caesar cipher, each letter in the plaintext is shifted by a fixed number of positions down or up the alphabet to produce the ciphertext.

Correct Answer: All of the above

TLS, SSL, and IPsec all use symmetric key encryption to secure communication between two parties, with the session key being negotiated via asymmetric methods.

Correct Answer: ECC

ECC (Elliptic Curve Cryptography) uses elliptic curves for encryption, digital signatures, and key exchange, offering equivalent security to RSA but with smaller key sizes.

Correct Answer: Dictionary attack

A dictionary attack involves trying commonly used passwords or words from a predefined list against a hashed password until the correct one is found.

Correct Answer: AES

AES is commonly used to secure communications in wireless networks under WPA2, providing strong encryption for protecting data over Wi-Fi.

Correct Answer: El Gamal

El Gamal relies on the difficulty of solving discrete logarithms, which makes it secure for encryption and digital signatures, but it requires longer key sizes than RSA.

Correct Answer: To list certificates that are no longer valid

A CRL lists certificates that have been revoked before their expiration date, allowing users and systems to avoid trusting certificates that have been compromised or are no longer valid.

Correct Answer: Elliptic Curve Cryptography (ECC)

ECC is widely used in blockchain technologies like Bitcoin due to its smaller key sizes, which provide efficient and secure cryptographic operations.

Correct Answer: 256 bits

SHA-256 generates a fixed-length hash output of 256 bits, providing a higher level of security compared to SHA-1 and MD5.

Correct Answer: Adding random data to a password before hashing

Salting involves adding random data to a password before hashing to prevent attackers from using precomputed hash values (rainbow tables) to crack the password.

Correct Answer: A key used to encrypt a single message or session

An ephemeral key is used for a single message or session and is discarded afterward, providing better security by ensuring that previous keys cannot be reused.

Correct Answer: It is faster and works well for real-time applications

Stream encryption is often faster than block encryption and works well for real-time applications like audio and video transmission, where data is processed bit by bit.