CYG Chapter 5 Fast Block Ciphers

NBS solicited proposals for a cs, choosing DES based on LUCIFER by IBM (Adler et al.)

Rumors say that IBM or the NSA installed trapdoor in DES

DES being published and starting a public discussion

DES adopted as a standard for unclassified applications

Last review of DES in a 5 years loop // Was dedicated for 10-15 years and proved to be more durable

K₀=(k₁, …,k₇,b₁,k₉, …,k₆₃,b₈) // 56 bits, extended by 8 (odd) parity bits for each 7 bits for error detection

1. Devide 56 key bits into 28 bits each C₀ and D₀

2. Generate C_n,D_n via cyclic leftshift by s_n from C_n-1,D_n-1 with n = 1,…,16 and s_n := {If n \in {1,2,9,16} then 1; else 2}

3. Of each (C_n,D_n) select 48 bit

1. Get IP of input bits and divide plaintext into blocks of 64 bits

2. Split into two blocks of 32 bits

3. 16 rounds of SBB

4. Obtain inverse IP^-1