Subversion Repositories apbtoaes128

//////////////////////////////////////////////////////////////////

////

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////    AES CORE BLOCK

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////

////

//// This file is part of the APB to I2C project

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//// http://www.opencores.org/cores/apbi2c/

////

////

////

//// Description

////

//// Implementation of APB IP core according to

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//// aes128_spec IP core specification document.

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////

////

//// To Do: Things are right here but always all block can suffer changes

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////

////

////

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//// Author(s): - Felipe Fernandes Da Costa, fefe2560@gmail.com

////              Julio Cesar 

////

///////////////////////////////////////////////////////////////// 

////

////

//// Copyright (C) 2009 Authors and OPENCORES.ORG

////

////

////

//// This source file may be used and distributed without

////

//// restriction provided that this copyright statement is not

////

//// removed from the file and that any derivative work contains

//// the original copyright notice and the associated disclaimer.

////

////

//// This source file is free software; you can redistribute it

////

//// and/or modify it under the terms of the GNU Lesser General

////

//// Public License as published by the Free Software Foundation;

//// either version 2.1 of the License, or (at your option) any

////

//// later version.

////

////

////

//// This source is distributed in the hope that it will be

////

//// useful, but WITHOUT ANY WARRANTY; without even the implied

////

//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR

////

//// PURPOSE. See the GNU Lesser General Public License for more

//// details.

////

////

////

//// You should have received a copy of the GNU Lesser General

////

//// Public License along with this source; if not, download it

////

//// from http://www.opencores.org/lgpl.shtml

////

////

///////////////////////////////////////////////////////////////////

module mix_columns

(

        // OUTPUTS

        output [31:0] mix_out_enc,

        output [31:0] mix_out_dec,

        // INPUTS

        input  [31:0] mix_in

);

localparam integer SIZE      = 32;

localparam integer WORD_SIZE = 8;

localparam integer NUM_WORDS = 4;

wire [WORD_SIZE - 1 : 0] col  [0 : NUM_WORDS - 1];

wire [WORD_SIZE - 1 : 0] sum_p[0 : NUM_WORDS - 1];

wire [WORD_SIZE - 1 : 0] y    [0 : NUM_WORDS - 2];

//=====================================================================================

// Multiplication by 02 in GF(2^8) 

//=====================================================================================

function [7:0] aes_mult_02;

  input [7:0] data_in;

  begin

    aes_mult_02 = (data_in << 1) ^ {8{data_in[7]}} & 8'h1b;

  end

endfunction

//=====================================================================================

// Multiplication by 04 in GF(2^8)

//=====================================================================================

function [7:0] aes_mult_04;

  input [7:0] data_in;

  begin

    aes_mult_04 = ((data_in << 2) ^ {8{data_in[6]}} & 8'h1b) ^ {8{data_in[7]}} & 8'h36;

  end

endfunction

//=====================================================================================

// Word to Byte transformation

//=====================================================================================

generate

        genvar i;

        for(i = 0 ; i < NUM_WORDS; i = i + 1)

                assign col[i] = mix_in[WORD_SIZE*(i + 1) - 1: WORD_SIZE*i];

endgenerate

//=====================================================================================

// Direct Mix Column Operation

//=====================================================================================

generate

        genvar j;

        for(j = 0; j < NUM_WORDS; j = j + 1)

                begin

                        assign sum_p[j] = col[(j + 1)%NUM_WORDS] ^ col[(j + 2)%NUM_WORDS] ^ col[(j + 3)%NUM_WORDS];

                        assign mix_out_enc[ WORD_SIZE*(j + 1) - 1 : WORD_SIZE*j] = aes_mult_02(col[j] ^ col[(j + NUM_WORDS - 1)%NUM_WORDS]) ^ sum_p[j];

                end

endgenerate

//=====================================================================================

// Inverse Mix Column Operation

//=====================================================================================

assign y[0] = aes_mult_04(col[2] ^ col[0]);

assign y[1] = aes_mult_04(col[3] ^ col[1]);

assign y[2] = aes_mult_02(  y[1] ^   y[0]);

assign mix_out_dec = mix_out_enc ^ {2{y[2] ^ y[1], y[2] ^ y[0]}};

endmodule