// TOTAL COMMANDER PUBLIC-KEY CRYPTOSYSTEM
// by DimitarSerg
// (2013)
function IsBit(Value, Pos: Integer): Boolean;
asm
  mov ECX,EAX
  xor EAX,EAX
  and EDX,31
  bt ECX,EDX
  adc EAX,0
end;

function count_bin_digits(a:integer):byte;
begin
  Result:=0;
  repeat
    Inc(Result);
    a := a div 2; //Remove the next least significant bit in the record number.
  until a = 0;
end;

function rsa_encrypt(cyphertext:string;e:Dword):string;
var n1,c1,r,r1,r2,c2,n_2fg:TFGInt;
c,n,n_2:string;
i:byte;
begin
    n:='AAD4474DC8387E81BB095D810F4F4F21D5D7CCC756E3D6E5DEE48AC000C25AA0EFAD0AD3A5AC46F15B50249597461BBB87CDC3F1BA37C17A9A207A3603E38E718F9927A5EB38005D8B72EAFDC63931C3D93C1FAD457A17CA85BEB40F3FA9152770DAC12E8E3B912D';
  n_2:='2';

  ConvertHexStringToBase256String(n_2,n_2);     // Convert N-2 to Base256
  Base256StringToFGInt(n_2,n_2fg);              // Convert N-2 to FGInt

  ConvertHexStringToBase256String(N,N);         // Convert N to Base256
  Base256StringToFGInt(N,n1);                   // Convert N to FGInt

  ConvertHexStringToBase256String(cyphertext,c);// Convert CT to Base256
  Base256StringToFGInt(c,c1);                   // Convert CT to FGInt

 r1:=c1;

for i:=count_bin_digits(e)-1 downto 1 do
 begin
     if IsBit(e,i) then
      begin
        FGIntMul(c1,c1,r);           //MUL
        FGIntSub(r,n_2fg,c2);        //ADD
      end;

     FGIntMul(c1,c2,r);           //MUL
     FGIntSub(r,r1,r2);           //ADD
     FGIntMod(r2,n1,c2);          //MOD

     FGIntMul(c1,c1,r);           //MUL
     FGIntSub(r,n_2fg,r2);        //ADD
     FGIntMod(r2,n1,c1);          //MOD
  end;

 //-----------------------------------------------
  FGIntToBase256String(c2,result);
  ConvertBase256StringToHexString(result,result);
  // Destroy FGInt (important!)
  FGIntDestroy(c2);
  FGIntDestroy(r);
  FGIntDestroy(r1);
  FGIntDestroy(r2);
  FGIntDestroy(n_2fg);
  FGIntDestroy(c1);
  FGIntDestroy(n1);
end;