LOOKING INSIDE AεS AND BεS

摘要

We analyze an algebraic representation of AεS -128 as an embedding in BεS, due to Murphy and Robshaw. We present two systems of equations S~* and K~* concerning encryption and key generation processes. After some simple but rather cumbersome substitutions, we should obtain two new systems C_1 and C_2. C_1 has 16 very dense equations of degree up to 255 in each of its 16 variables. With a single pair (p,c), with p a cleartext and c its encryption, its roots give all possible keys that should encrypt p to c. C_2 may be defined using 11 or more pairs (p,c), and has 16 times as many equations in 176 variables. K~* and most of S~* is invariant for all key choices.