type
    TByteArray = array of Byte;

procedure RC4(Data, Key: Pointer; DataSize: DWORD; KeySize: BYTE); overload;
var
    Temp: BYTE;
    Result: PBYTE;
    X, Y, Z: DWORD;
    RB: array[BYTE] of DWORD;
begin
    if Assigned(Data) and (Assigned(Key)) and (KeySize>0) then
    try
       for X:=0 to 255 do
          RB[X]:=X;
       X:=0;
       Y:=0;
       Z:=0;
       for X:=0 to 255 do
       begin
          Y:=(Y+RB[X]+(TByteArray(Key)[X mod KeySize])) mod 256;
          Temp:=RB[X];
          RB[X]:=RB[Y];
          RB[Y]:=Temp;
       end;
       X:=0;
       Y:=0;
       Z:=0;
       Result:=Data;
       for X:=0 to (DataSize-1) do
       begin
          Y:=(Y+1) mod 256;
          Z:=(Z+RB[Y]) mod 256;
          Temp:=RB[Y];
          RB[Y]:=RB[Z];
          RB[Z]:=Temp;
          Result^:=Result^ xor (RB[(RB[Y]+RB[Z]) mod 256]);
          Inc(Result);
       end;
    except
    end;
end;

function RC4(Str: string; Key: string): string; overload;
begin
    Result:=Str;
    RC4(@Result[1], @Key[1], (Length(Result)), (Length(Key)));
end;