SB 7: Cryptographic Methods and Weaknesses

Question 1

Describe the one-time-pad

Answer 1

1. The key must be at least as long as the plaintext
2. The key must be random and patternless
3. The key must never be reused, either in part or as a whole
4. The key must be completely secret

The problem with secure key distribution makes them impractical. They have been mathematically proven to be impossible to break provided they follow the rules of key generation.

Question 2

What is steganography?

Answer 2

A way to hide the existence of data. Can encode the data into something else like a picture. Or constantly send rubbish between parties so the important data gets “lost” among the rubbish.

Question 3

What is traffic analysis?

Answer 3

Analyzing data traffic and thus discovering the existence of information being exchanged between some parties. Does not give the contents of the information.

Question 4

What is the Vigenère cipher?

Answer 4

A poly-alphabetic cipher, it uses multiple alphabets to generate the ciphertext. The key (i.e MAGGIE) is a sequence of letters that are then applied to successive plaintext characters, the key is repeated over the entire plaintext.
Weakness: the repeating nature of the key

Question 5

What are some problems with symmetric cryptosystems/keys?

Answer 5

Moving the key, if an unauthorized party gets hold of the key as it is being “moved” they have the power to decrypt any data that has been encrypted with that specific key. Using a separate channel to move the key could fix the problem (dissociates the key and the data?).
Sending to multiple people requires multiple keys to be used and then sent, many keys to keep track of.

Question 6

What is defense in depth?

Answer 6

Leverages multiple security measures to protect (an organization’s) assets