Types of Security

Question 1

Unconditional security

Answer 1

The uncertainty in the plaintext, after observing the ciphertext, must be equal to the a priori uncertainty about the plaintext. Observation of the ciphertext provides no information to an adversary.

This means that the uncertainty in the plaintext,
after observing the ciphertext, must be equal to the
a priori uncertainty about the plaintext.

Observation of the ciphertext provides no
information to an adversary.

Question 2

Computational security

Answer 2

level of computation required to defeat it (using
best attack known)&raquo_space; the computational resources
of the adversary.