Encryption Fundamentals

Question 1

DES

Answer 1

Data Encryption Standard, 56-bit key, 64-bit block cipher, insecure due to brute-force vulnerability.

Question 2

3DES

Answer 2

Triple DES applies DES three times, more secure than DES but slower and outdated.

Question 3

AES

Answer 3

Advanced Encryption Standard, supports 128/192/256-bit keys, widely used and secure.

Question 4

RC4

Answer 4

Stream cipher in the RC family, deprecated due to keystream bias and insecurity.

Question 5

RC5

Answer 5

Block cipher with variable block size, key size, and number of rounds.

Question 6

RC6

Answer 6

Advanced block cipher based on RC5, finalist in AES competition.

Question 7

RSA

Answer 7

Public key cryptosystem based on factoring large prime numbers, used for encryption and digital signatures.

Question 8

DSA

Answer 8

Digital Signature Algorithm, used only for digital signatures, based on discrete logarithms.

Question 9

ECC

Answer 9

Elliptic Curve Cryptography, efficient public-key system with smaller keys than RSA.

Question 10

ECDSA

Answer 10

Elliptic Curve Digital Signature Algorithm, variant of DSA using ECC.

Question 11

ElGamal

Answer 11

Asymmetric encryption scheme based on Diffie-Hellman, supports encryption and signatures.

Question 12

ECB

Answer 12

Electronic Codebook Mode, simple but insecure as it reveals patterns.

Question 13

CBC

Answer 13

Cipher Block Chaining Mode, uses IV and XOR to chain encryption.

Question 14

CTR

Answer 14

Counter Mode, turns block cipher into stream cipher using counters.

Question 15

GCM

Answer 15

Galois/Counter Mode, combines encryption and authentication.

Question 16

CFB

Answer 16

Cipher Feedback Mode, stream cipher mode using block cipher.

Question 17

OFB

Answer 17

Output Feedback Mode, another stream-like mode avoiding error propagation.

Question 18

MAC

Answer 18

Message Authentication Code, ensures data integrity and authenticity with a shared secret.

Question 19

HMAC

Answer 19

Keyed-hash MAC using hash functions like SHA-256 for strong integrity checks.

Question 20

AEAD

Answer 20

Authenticated Encryption with Associated Data, provides confidentiality and integrity.

Question 21

Diffie-Hellman

Answer 21

Key exchange method allowing two parties to establish a shared secret.

Question 22

ECDH

Answer 22

Elliptic Curve Diffie-Hellman, efficient key exchange over ECC.

Question 23

PFS

Answer 23

Perfect Forward Secrecy, ensures compromise of long-term keys doesn’t affect past sessions.

Question 24

DHE

Answer 24

Ephemeral Diffie-Hellman, supports PFS by generating temporary keys per session.

Question 25

IKE

Answer 25

Internet Key Exchange, protocol used to set up security associations in IPsec.

Question 26

ISAKMP

Answer 26

Internet Security Association and Key Management Protocol, works with IKE.

Question 27

Steganography

Answer 27

Concealing messages within other media, like images or audio.

Question 28

Obfuscation

Answer 28

Making code or communication harder to understand but not encrypted.

Question 29

Quantum Cryptography

Answer 29

Uses quantum mechanics for secure communication, like QKD.

Question 30

Post-Quantum Cryptography

Answer 30

Algorithms resistant to quantum attacks (e.g., lattice-based).

Question 31

Homomorphic Encryption

Answer 31

Allows computations on encrypted data without decryption.

Question 32

Format-Preserving Encryption

Answer 32

Encrypts data while keeping format intact (e.g., credit card numbers).

Question 33

SHA-2

Answer 33

Secure Hash Algorithm 2, family including SHA-256, widely used.

Question 34

SHA-3

Answer 34

Latest secure hash function standard, different construction than SHA-2.

Question 35

Salting

Answer 35

Adds randomness to password hashes to prevent precomputed attacks.

Question 36

PBKDF2

Answer 36

Key derivation function using multiple hash iterations to harden passwords.

Question 37

Argon2

Answer 37

Memory-hard KDF, winner of the Password Hashing Competition.

Question 38

Digital Signature

Answer 38

Cryptographic method of proving message authenticity and integrity.

Question 39

X.509 Certificate

Answer 39

Standard format for public key certificates.

Question 40

PKI

Answer 40

Public Key Infrastructure, framework to manage digital certificates.

Question 41

Key Rotation

Answer 41

Regularly changing cryptographic keys to limit exposure.

Question 42

Key Escrow

Answer 42

Storing encryption keys with a third party for recovery or access.

Question 43

Key Exchange

Answer 43

Securely transferring cryptographic keys between parties.