martes, 16 de octubre de 2012

Algoritmos Bloque/Bloque ciphers

Who and Where?
The new Block Cipher Rainbow, is the title of an article written by Chang-Hyi Lee and Jeong-Soo Kim in the  Samsung Advance Institute of Technology.

Type of math
Where propose another model of Block Cipher. This type of cipher has the substitution and permutation. similar to the block ciphers Square and SHARK 

In the article, the authors mention:
"the motivation for develop the algorithm came out from the hope that, first, the block cipher has the structure of parallelism, second, it has a self-reciprocal structure and third its round encryption  involves no linear and efficient key dependent diffusion layer".
The authors implement the algorithm and obtain that the proposal its acceptable, encrypting of 9 to 10mb/secs on a 133 MHz Pentium PC.

How it works?
This type of cipher works by 3 layers related to the round key active diffution and the others ones relates to the non linear sustitution with simple permutation.

Where Xi are 32 bit subblocks and K be a 128 bit round key and  \oplus denotes bit by bit logic XOR.

Taking that x and k are the same that the previous.

Where ^ denotes bit by bit logic AND.

This function consists in 3 types of components functions, P1, P2, P3, which all are defined in the following as functions of the sub-data block, GF(2³²) to GF(2³²). Let x = (x3, x2, x1, x0), Xi \in GF(2⁸) and so x \in GF(2³²). Let's define:

f be a bijective nonlinear function of GF(2⁸) to GF(2⁸)

f and f⁻¹ tables:


Searching I found that this type of cipher is mentioned by hackers for auditories of passwords and aplicated in telecommunications between satellites and smart cards.


1 comentario:

  1. Medio Spanglish el asunto. Faltó trabajar un ejemplo, igual como claridad y formato de presentación... Van 4 puntos de los 7 máximo.