Serious Cryptography

Question 1

What is important of the One-Time Pad cipher?

Answer 1

Randomness of a key with the size of the plaintext is the perfect security. This allows the attacker to not know anything beyond the size of the plaintext/ciphertext

Question 2

What are the downsides of the One-Time Pad?

Answer 2

The key has to be the same size as the plaintext and it can only be used once. Becomes impractical.

Question 3

What are the Main components of a cipher?

Answer 3

Permutation - Function that transforms the item
Mode of Operation - Algorithm using permutation process on the arbitrary plaintext/ciphertext

Question 4

Passive Attack Model

Answer 4

A perpetrator that is surreptitiously (secretively) collecting data but not trying to alter the system.

Question 5

How Does Authentication Encryption work? Is it Symmetric or Asymmetric?

Answer 5

Authenticated Encryption = Symmetric Encryption into CipherText with Authentication “Tag”. Decrypt only if the Tag is the correct one. Tag is only known with the Key.