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

////                                                             ////

////  DES                                                        ////

////  DES Top Level module                                       ////

////                                                             ////

////  Author: Rudolf Usselmann                                   ////

////          rudi@asics.ws                                      ////

////                                                             ////

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

////                                                             ////

//// Copyright (C) 2001 Rudolf Usselmann                         ////

////                    rudi@asics.ws                            ////

////                                                             ////

//// 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 SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     ////

//// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   ////

//// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   ////

//// FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR      ////

//// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,         ////

//// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES    ////

//// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE   ////

//// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR        ////

//// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF  ////

//// LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT  ////

//// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT  ////

//// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE         ////

//// POSSIBILITY OF SUCH DAMAGE.                                 ////

////                                                             ////

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

module des3(desOut, desIn, key1, key2, key3, decrypt, roundSel, clk);

output  [63:0]   desOut;

input   [63:0]   desIn;

input   [55:0]   key1;

input   [55:0]   key2;

input   [55:0]   key3;

input           decrypt;

input   [5:0]    roundSel;

input           clk;

wire    [1:48]  K_sub;

wire    [1:64]  IP, FP, tmp;

reg     [1:64]  FP_R;

reg     [1:32]  L, R;

wire    [1:32]  Xin;

wire    [1:32]  Lout;

wire    [1:32]  Rout;

wire    [1:32]  out;

//assign Lout = (roundSel == 0) ? IP[33:64] : R;

//assign Xin  = (roundSel == 0) ? IP[01:32] : L;

assign Lout =   (roundSel == 0) ? IP[33:64] :

                (       (roundSel == 16) ? FP_R[33:64] :

                        (       (roundSel == 32) ? FP_R[33:64] :

                                        R       ));

assign Xin  =   (roundSel == 0) ? IP[01:32] :

                (       (roundSel == 16) ? FP_R[01:32] :

                        (       (roundSel == 32) ? FP_R[01:32] :

                                        L       ));

/*

always @(roundSel or IP or tmp or R or FP)

        case(roundSel)

                6'h0:   Lout = IP[33:64];

                6'h10:  Lout = FP[33:64];

                6'h20:  Lout = FP[33:64];

                default: Lout = R;

        endcase

always @(roundSel or IP or tmp or L or FP)

        case(roundSel)

                6'h0:   Xin = IP[01:32];

                6'h10:  Xin = FP[01:32];

                6'h20:  Xin = FP[01:32];

                default: Xin = L;

        endcase

*/

always @(posedge clk)

        FP_R <= #1 FP;

assign Rout = Xin ^ out;

assign FP = { Rout, Lout};

crp u0( .P(out), .R(Lout), .K_sub(K_sub) );

always @(posedge clk)

        L <= #1 Lout;

always @(posedge clk)

        R <= #1 Rout;

// Select a subkey from key.

key_sel3 u1(

        .K_sub(         K_sub           ),

        .key1(          key1            ),

        .key2(          key2            ),

        .key3(          key3            ),

        .roundSel(      roundSel        ),

        .decrypt(       decrypt         )

        );

assign tmp[1:64] = {    desOut[06], desOut[14], desOut[22], desOut[30], desOut[38], desOut[46],

                        desOut[54], desOut[62], desOut[04], desOut[12], desOut[20], desOut[28],

                        desOut[36], desOut[44], desOut[52], desOut[60], desOut[02], desOut[10],

                        desOut[18], desOut[26], desOut[34], desOut[42], desOut[50], desOut[58],

                        desOut[00], desOut[08], desOut[16], desOut[24], desOut[32], desOut[40],

                        desOut[48], desOut[56], desOut[07], desOut[15], desOut[23], desOut[31],

                        desOut[39], desOut[47], desOut[55], desOut[63], desOut[05], desOut[13],

                        desOut[21], desOut[29], desOut[37], desOut[45], desOut[53], desOut[61],

                        desOut[03], desOut[11], desOut[19], desOut[27], desOut[35], desOut[43],

                        desOut[51], desOut[59], desOut[01], desOut[09], desOut[17], desOut[25],

                        desOut[33], desOut[41], desOut[49], desOut[57] };

// Perform initial permutation

assign IP[1:64] = {     desIn[06], desIn[14], desIn[22], desIn[30], desIn[38], desIn[46],

                        desIn[54], desIn[62], desIn[04], desIn[12], desIn[20], desIn[28],

                        desIn[36], desIn[44], desIn[52], desIn[60], desIn[02], desIn[10],

                        desIn[18], desIn[26], desIn[34], desIn[42], desIn[50], desIn[58],

                        desIn[00], desIn[08], desIn[16], desIn[24], desIn[32], desIn[40],

                        desIn[48], desIn[56], desIn[07], desIn[15], desIn[23], desIn[31],

                        desIn[39], desIn[47], desIn[55], desIn[63], desIn[05], desIn[13],

                        desIn[21], desIn[29], desIn[37], desIn[45], desIn[53], desIn[61],

                        desIn[03], desIn[11], desIn[19], desIn[27], desIn[35], desIn[43],

                        desIn[51], desIn[59], desIn[01], desIn[09], desIn[17], desIn[25],

                        desIn[33], desIn[41], desIn[49], desIn[57] };

// Perform final permutation

assign desOut = {       FP[40], FP[08], FP[48], FP[16], FP[56], FP[24], FP[64], FP[32],

                        FP[39], FP[07], FP[47], FP[15], FP[55], FP[23], FP[63], FP[31],

                        FP[38], FP[06], FP[46], FP[14], FP[54], FP[22], FP[62], FP[30],

                        FP[37], FP[05], FP[45], FP[13], FP[53], FP[21], FP[61], FP[29],

                        FP[36], FP[04], FP[44], FP[12], FP[52], FP[20], FP[60], FP[28],

                        FP[35], FP[03], FP[43], FP[11], FP[51], FP[19], FP[59], FP[27],

                        FP[34], FP[02], FP[42], FP[10], FP[50], FP[18], FP[58], FP[26],

                        FP[33], FP[01], FP[41], FP[09], FP[49], FP[17], FP[57], FP[25] };

endmodule