Question 91 - 212-81 discussion

Total Break

https://en.wikipedia.org/wiki/Cryptanalysis

The results of cryptanalysis can also vary in usefulness. For example, cryptographer Lars Knudsen (1998) classified various types of attack on block ciphers according to the amount and quality of secret information that was discovered:

Total break --- the attacker deduces the secret key.

Global deduction --- the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key.

Instance (local) deduction --- the attacker discovers additional plaintexts (or ciphertexts) not previously known.

Information deduction --- the attacker gains some Shannon information about plaintexts (or ciphertexts) not previously known.

Distinguishing algorithm --- the attacker can distinguish the cipher from a random permutation.

Incorrect answers:

Shannon's Entropy - average level of 'information', 'surprise', or 'uncertainty' inherent in the variable's possible outcomes. The concept of information entropy was introduced by Claude Shannon in his 1948 paper 'A Mathematical Theory of Communication'.

Avalanche effect - the desirable property of cryptographic algorithms, typically block ciphers and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip). In the case of high-quality block ciphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext.