Criptografador

unit Unit1;

    {$mode objfpc}{$H+}

    interface

    uses

      Classes, SysUtils, FileUtil, Forms,

    Controls, Graphics, Dialogs, StdCtrls;

    type

      { TForm1 }

      TForm1 = class(TForm)

        Button1: TButton;

        Button2: TButton;

        edtcriptografado: TEdit;

        edttexto: TEdit;

        edtdescriptografado: TEdit;

        edtkey: TEdit;

        Label1: TLabel;

        Label2: TLabel;

        Label3: TLabel;

        Label4: TLabel;

        procedure Button1Click(Sender: TObject);

        procedure Button2Click(Sender: TObject);

        procedure FormCreate(Sender: TObject);

      private

       function criptografar(const key, texto:String):String;

       function descriptografar(const key, texto:String):String;

      public

      end;

    var

      Form1: TForm1;

    implementation


    {$R *.lfm}


    { TForm1 }


    procedure TForm1.Button1Click(Sender: TObject);

    begin

     edtcriptografado.Text:=criptografar(edtkey.Text,edttexto.Text);

    end;

    procedure TForm1.Button2Click(Sender: TObject);

    begin

     edtdescriptografado.Text:=descriptografar(edtkey.Text,

    edtcriptografado.Text);

    end;

    function TForm1.criptografar(const key, texto: String): String;

    var

      I: Integer;

      C: Byte;

    begin

      Result := '';

      for I := 1 to Length(texto) do begin

        if Length(Key) > 0 then

          C := Byte(Key[1 + ((I - 1) mod Length(Key))]) xor Byte(texto[I])

        else

          C := Byte(texto[I]);

        Result := Result + AnsiLowerCase(IntToHex(C, 2));

      end;


    end;


    function TForm1.descriptografar(const key, texto: String): String;

    var

      I: Integer;

      C: Char;


    begin

      Result := '';

      for I := 0 to Length(texto) div 2 - 1 do begin

        C := Chr(StrToIntDef('$' + Copy(texto, (I * 2) + 1, 2), Ord(' ')));

        if Length(Key) > 0 then

          C := Chr(Byte(Key[1 + (I mod Length(Key))]) xor Byte(C));

        Result := Result + C;

      end;

    end;


    end.