Chapter 2 Crypto Basics Problems: 1, 2, 3, 7, 8, 9, 13, 18, 20
Kerckhoffs principle: The inner workings of the cryptosystems are completely known by the attacker, the only secret is the key. Classic crypto:
1929: Gentlemen do not read each other`s mail Confusion: (simple substitution and a onetime pad) Obscure the relationship between the plaintext and the ciphertext. Diffusion: (double transposition) Supposed to spread the plaintext statistics through the ciphertext. Diffusion alone is not enough to be probable secure. Onetime pad has both. If you use codebook and permutation then you use both. Stream cipher: Better in hardware Block cipher: Better in software
