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////////////////////////////////////////////////////////////////// ////
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//// ////
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//// AES Decryption Core for FPGA ////
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//// ////
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//// This file is part of the AES Decryption Core for FPGA project ////
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//// http://www.opencores.org/cores/xxx/ ////
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//// ////
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//// Description ////
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//// Implementation of AES Decryption Core for FPGA according to ////
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//// core specification document. ////
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//// ////
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//// To Do: ////
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//// - ////
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//// ////
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//// Author(s): ////
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//// - scheng, schengopencores@opencores.org ////
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//// ////
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//////////////////////////////////////////////////////////////////////
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//// ////
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//// Copyright (C) 2009 Authors and OPENCORES.ORG ////
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//// ////
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//// This source file may be used and distributed without ////
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//// restriction provided that this copyright statement is not ////
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//// removed from the file and that any derivative work contains ////
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//// the original copyright notice and the associated disclaimer. ////
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//// ////
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//// This source file is free software; you can redistribute it ////
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//// and/or modify it under the terms of the GNU Lesser General ////
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//// Public License as published by the Free Software Foundation; ////
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//// either version 2.1 of the License, or (at your option) any ////
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//// later version. ////
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//// ////
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//// This source is distributed in the hope that it will be ////
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//// useful, but WITHOUT ANY WARRANTY; without even the implied ////
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//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////
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//// PURPOSE. See the GNU Lesser General Public License for more ////
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//// details. ////
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//// ////
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//// You should have received a copy of the GNU Lesser General ////
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//// Public License along with this source; if not, download it ////
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//// from http://www.opencores.org/lgpl.shtml ////
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//// //// ///
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///////////////////////////////////////////////////////////////////
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//// ////
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//// This module computes one column of the InvMixColumns() defined ////
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//// in section 5.3.3 in FIPS-197 specification. ////
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//// ////
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////////////////////////////////////////////////////////////////////////
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module InvMixCol_slice(
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input [7:0] S0c,
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input [7:0] S1c,
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input [7:0] S2c,
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input [7:0] S3c,
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input bypass,
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output [31:0] new_S);
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wire [7:0] S0cx9, S0cxb, S0cxd, S0cxe;
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wire [7:0] S1cx9, S1cxb, S1cxd, S1cxe;
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wire [7:0] S2cx9, S2cxb, S2cxd, S2cxe;
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wire [7:0] S3cx9, S3cxb, S3cxd, S3cxe;
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wire [7:0] sum0, sum1, sum2, sum3;
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// GF multipliers to generate products for x9, xb, xd, xe
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gfmul_inv gfmul_inv_u0(.d(S0c), .x2(), .x3(), .x9(S0cx9), .xb(S0cxb), .xd(S0cxd), .xe(S0cxe));
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gfmul_inv gfmul_inv_u1(.d(S1c), .x2(), .x3(), .x9(S1cx9), .xb(S1cxb), .xd(S1cxd), .xe(S1cxe));
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gfmul_inv gfmul_inv_u2(.d(S2c), .x2(), .x3(), .x9(S2cx9), .xb(S2cxb), .xd(S2cxd), .xe(S2cxe));
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gfmul_inv gfmul_inv_u3(.d(S3c), .x2(), .x3(), .x9(S3cx9), .xb(S3cxb), .xd(S3cxd), .xe(S3cxe));
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// Compute InvMixColumns according to section 5.3.3 of FIPS-197 spec.
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// Feed input through directly when bypass=1.
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assign sum0 = bypass ? S0c : S0cxe ^ S1cxb ^ S2cxd ^ S3cx9;
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assign sum1 = bypass ? S1c : S0cx9 ^ S1cxe ^ S2cxb ^ S3cxd;
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assign sum2 = bypass ? S2c : S0cxd ^ S1cx9 ^ S2cxe ^ S3cxb;
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assign sum3 = bypass ? S3c : S0cxb ^ S1cxd ^ S2cx9 ^ S3cxe;
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assign new_S = {sum0, sum1, sum2, sum3};
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endmodule
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