Symmetric Encryption

Question 1

What is RC4?

Answer 1

Rivest Cipher 4, a symmetric stream cipher able to use between 40 and 2,048 bit-keys. AES recommended over RC4.

Question 2

What is DES?

Answer 2

Data Encryption Standard, a symmetric block cipher, encrypting data in 64-bit blocks. Can only use a key of 56-bits, not recommended for use today.

Question 3

What is 3DES?

Answer 3

Triple Data Encryption Standard, takes DES and encrypts data with it 3 times, in 64-bit blocks. Could be using three keys, two keys, or the same key three times. Can use key sizes of 56, 112, or 168 bits.

Question 4

What is AES?

Answer 4

Advanced Encryption Standard, a strong symmetric block cipher, encrypting data in 128-bit blocks. Very fast, efficient, and strong. Can use 128-, 192-, or 256-bit keys.

Question 5

What is Blowfish?

Answer 5

Blowfish, a symmetric block cipher encrypting in 64-bit blocks with a “variable length key” (32 to 448 bits). Faster than AES-256.

Very secure; no known way to break the full 16 rounds of encryption. Also not limited to patents (anyone can use it!)

Question 6

What is Twofish?

Answer 6

Twofish, symmetric block cipher encrypting in 128-bit blocks. Uses a 128-bit block size, and supports 128-, 192-, or 256-bit keys. Also not patented (anyone can use it).

Question 7

Which encryption algorithms are symmetric algorithms?

Answer 7

RC4, DES, 3DES, Blowfish, Twofish, and AES.

Question 8

Symmetric encryption differs from asymmetric in which way?

Answer 8

Symmetric encryption only uses 1 key.

Question 9

What is RSA?

Answer 9

An encryption algorithm, using a public-key cryptography system to encrypt and decrypt.

Question 10

What is Diffie-Hellman key exchange?

Answer 10

A method used to exchange keys over an insecure network. Does not encrypt or authenticate, just sends keys and protects the key.

Question 11

Where is Diffie-Hellman key exchange used?

Answer 11

In Perfect Forward Secrecy (PFS). In PFS, Ephemeral Diffie-Hellman is used (keys will only be used for a short period of time), combined with elliptic curve cryptography (ECC) to encrypt.

PFS is AKA as ECDHE.

Question 12

What is PFS also known as?

Answer 12

ECDHE

Question 13

What does PFS do?

Answer 13

Perfect Forward Secrecy is a key exchange method.

Question 14

In a data stream where the amount of data is unknown, which type of cipher is more efficient?

Answer 14

Stream Ciphers

Question 15

In a data stream where the amount of data is known, which type of cipher is more efficient?

Answer 15

Block Ciphers

Question 16

AES-256 indicates what?

Answer 16

AES using a 256-bit key

Question 17

Which key sizes can AES use?

Answer 17

128, 192, or 256

Question 18

What is recommended over RC4?

Answer 18

AES

Question 19

In computer applications, where is a one-time pad used?

Answer 19

Tokens or fobs