type
  TRC4Context = record
    D: array[Byte] of Byte;
    I,J: Byte;
  end;

procedure RC4Init(var RC4: TRC4Context; const Key: String);
var
  R,S,T,U: Byte;
  L: Integer;
begin
  L := Length(Key);
  with RC4 do
  begin
    I := 0;
    J := 0;
    for S := 0 to 255 do D[S] := S;
    R := 0;
    U := 1;
    for S := 0 to 255 do
    begin
      Inc(R, D[S] + Ord(Key[U]));
      T := D[S];
      D[S] := D[R];
      D[R] := T;
      Inc(U);
      if U > L then U := 1;
    end;
  end;
end;

procedure RC4Code(var RC4: TRC4Context; const Source; var Dest; Count: Integer); overload;
var
  S: Integer;
  T: Byte;
begin
  with RC4 do
    for S := 0 to Count -1 do
    begin
      Inc(I);
      T := D[I];
      Inc(J, T);
      D[I] := D[J];
      D[J] := T;
      Inc(T, D[I]);
      TByteArray(Dest)[S] := TByteArray(Source)[S] xor D[T];
    end;
end;

procedure RC4Done(var RC4: TRC4Context);
begin
  FillChar(RC4, SizeOf(RC4), 0);
end;

function RC4Code(const Value, Password: String): String; overload;
var
  RC4: TRC4Context;
  Len: Integer;
begin
  RC4Init(RC4, Password);
  try
    Len := Length(Value);
    SetLength(Result, Len);
    RC4Code(RC4, Value[1], Result[1], Len);
  finally
    RC4Done(RC4);
  end;
end;

function BinToHexStr(const Value: String): String;
var
  Size: Integer;
begin
  Size := Length(Value);
  SetLength(Result, Size * 2);
  BinToHex(PChar(Value), PChar(Result), Size);
end;

function HexToBinStr(const Value: String): String;
var
  Size: Integer;
begin
  Size := (Length(Value) +1) div 2;
  SetLength(Result, Size);
  HexToBin(PChar(Value), PChar(Result), Size);
end;

function Encode(const Value, Password: String): String;
begin
  Result := BinToHexStr(RC4Code(Value, Pasword));
end;

function Decode(const Value, Password: String): String;
begin
  Result := RC4Code(HexToBinStr(Value), Password);
end;