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

////                                                             ////

////  Tripple DES                                                ////

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

////                                                             ////

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

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

////                                                             ////

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

////                                                             ////

//// Copyright (C) 2002 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, clk);

output  [63:0]   desOut;

input   [63:0]   desIn;

input   [55:0]   key1;

input   [55:0]   key2;

input   [55:0]   key3;

input           decrypt;

input           clk;

wire    [55:0]   key_a;

wire    [55:0]   key_b;

wire    [55:0]   key_c;

wire    [63:0]   stage1_out, stage2_out;

reg     [55:0]   key_b_r [16:0];

reg     [55:0]   key_c_r [33:0];

integer         i;

assign key_a = decrypt ? key3 : key1;

assign key_b = key2;

assign key_c = decrypt ? key1 : key3;

always @(posedge clk)

        key_b_r[0] <= #1 key_b;

always @(posedge clk)

        for(i=0;i<16;i=i+1)

                key_b_r[i+1] <= #1 key_b_r[i];

always @(posedge clk)

        key_c_r[0] <= #1 key_c;

always @(posedge clk)

        for(i=0;i<33;i=i+1)

                key_c_r[i+1] <= #1 key_c_r[i];

des u0( .desOut(stage1_out),    .desIn(desIn),          .key(key_a), .decrypt(decrypt), .clk(clk) );

des u1( .desOut(stage2_out),    .desIn(stage1_out),     .key(key_b_r[16]), .decrypt(!decrypt), .clk(clk) );

des u2( .desOut(desOut),        .desIn(stage2_out),     .key(key_c_r[33]), .decrypt(decrypt),   .clk(clk) );

endmodule