Week 5

Question 1

What is a Block Cipher?

Answer 1

Encrypts data in specific-sized blocks, such as 64/128-bit blocks.

Question 2

What is a Stream Cipher?

Answer 2

Encrypts data as a stream of bytes rather than dividing it into blocks.

Question 3

What is Padding?

Answer 3

Adding data to the beginning, middle, or end of a message before encrypting the message

Question 4

List and Explain 3 Padding Schemes

Answer 4

1- CMS (Pads with the same value of the number of padding bytes)
2- Bits (This pads with 80 followed by zero bytes)
3- Null (This pads with NULL bytes. This is only used with ASCII text)

Question 5

List 3 Secret Key methods

Answer 5

1 DES
2 AES
3 Blowfish

Question 6

List and Explain 4 Salting methods

Answer 6

1- ECB Messages encrypted on a block-by-block basis
2- CBC
3- CFB
4- OFB

Question 7

Why is it important to understand the length of time a message takes to crack?

Answer 7

The message may need to be kept a secret for a certain time period.

Question 8

Explain what the Stream cipher RC4 is?

Answer 8

Used in wireless communications

Question 9

What is the Diffie-Hellman protocol?

Answer 9

A way of generating a shared secret between two people in such a way that the secret can’t be seen by observing the communication.