Lecture 2 - Secret Key Encryption

Question 1

What does hashing provide?

Answer 1

Integrity

Question 2

Digital certs or PKIs provide what?

Answer 2

Authentication

Question 3

Asymmetric encryption provides what?

Answer 3

Key exchange

Question 4

Symmetric encryption provides what?

Answer 4

Confidentiality

Question 5

E-voting, or crypto is meant to provide what?

Answer 5

Anonymity

Question 6

Secret key encryption is also known as symmetric encryption. What does this mean?

Answer 6

Symmetric encryption uses the same key for encryption & decryption

Question 7

Public key encryption is known as asymmetric encryption. What does this mean?

Answer 7

Asymmetric encryption uses different keys (public & private) for encryption and decryption

Question 8

List some characteristics of symmetric encryption?

Answer 8

1. Uses the same key
2. Extremely fast
3. Uses smaller keys
4. Key exchange is a problem
5. Only offers confidentiality

Question 9

List some characteristics of asymmetric encryption?

Answer 9

1. Use different key (public / private)
2. Relatively slow
3. Bigger keys
4. Good at key exchange
5. Offers confidentiality and authentication

Question 10

3-DES, RC4, RC5, AES are examples of what type of encryption

Answer 10

Symmetric encryption

Question 11

DH, RSA, EIGamal, DSA are examples of what type of encryption

Answer 11

Asymmetric encryption

Question 12

What is the Diffie-Hellman key exchange?

Answer 12

The Diffie-Hellman key exchange was the first widely used method of safely developing and exchanging keys over an insecure channel.

Question 13

What is a one-way function in cryptography?

Answer 13

It is easy to compute, but hard to invert.

Question 14

What is a prime number

Answer 14

A prime number is one that is divisible by itself and 1 only

Question 15

Be able to write out the Diffie-Helman two step algorithm

Answer 15

A = Gx mod (p)
B = Gy mod (p)

Bob shared key = Bx mod (p)
Alice shared key = Ax mod (p)

Question 16

Encryption can be categorised as ______ and ______ based

Answer 16

Encryption can be categorised as Stream and Block based

Question 17

List two examples of Stream Based encryption

Answer 17

RC4 and ChaCha

Question 18

List some examples of Block Based encryption

Answer 18

RC2, RC5, DES, AES, Blowfish

Question 19

In terms of key sizes and attacks, what is the main weakness against ciphers?

Answer 19

Brute forcing keys is the main weakness against most ciphers

Question 20

In terms of “Key Management”, list three methods to share keys

Answer 20

1. Offline distribution such as snail mail
2. Public key encryption
3. Diffie Helman

Question 21

In terms of symmetric ciphers, what is the block size and key size for AES

Answer 21

1. Block size = 128
2. Key size = 128,192,256

Question 22

In terms of symmetric ciphers, what is the block size and key size for DES

Answer 22

1. Block size = 64
2. Key size = 56

Question 23

In terms of symmetric ciphers, what is the block size and key size for 3DES

Answer 23

1. Block size = 64
2. Key size = 112 or 168