///////////////////////////////////////////////////
///////////////////Шифр ////////////////////////
///////////////////////////////////////////////////
unit ;
var
  s: array [0..255] of Byte;
 i,j: Byte;
//Инициализация S-Box'а
procedure InitCipher(key: ShortString);
var
  k: array [0..255] of Byte;
  t: Byte;
  l: Cardinal;
 i0,j0: Byte;
begin
 for i0 := 0 to 255 do s[i0] := i0;
 j0 := 1; l := Length(key);
 for i0 := 0 to 255 do
  begin
  k[i0] := Ord(key[j0]);
  if j0 = l then j0 := 0;
  Inc(j0);
  end;
 for i0 := 0 to 255 do
  begin
  j0 := (j0 + k[i0] + s[i0]) mod 256;
  t := s[i0];
  s[i0] := s[j0];
  s[j0] := t;
  end;
 i := 0;
 j := 0;
end;
//Шифрование конкретного символа
function GetByteCiphered(bt: Byte): Byte;
var
 t: Byte;
begin
 i := (i + 1) mod 256;
 j := (j + s[i]) mod 256;
 t := s[i];
 s[i] := s[j];
 s[j] := t;
 t := (s[i] + s[j]) mod 256;
 Result := bt XOR s[t];
end;
//Применения шифра к данным потока
function ApplyToData(InitialData: TStream; var Buffer: TStream; key: ShortString): Boolean; stdcall;
var
 i: Cardinal;
 d: Byte;
begin
 if (key = '')OR(Buffer = InitialData)OR(Buffer = nil)OR(InitialData = nil)OR(InitialData.Size = 0)OR(Buffer.Size <> 0) then
  begin
  Result := false;
  Exit;
  end;
 InitCipher(key);
 try
  InitialData.Position := 0;
  for i := 0 to InitialData.Size-1 do
  begin
  InitialData.ReadBuffer(d,1);
  d := GetByteCiphered(d);
  Buffer.WriteBuffer(d,1);
  end;
 except
  Result := false;
  Exit;
 end;
 InitialData.Position := 0;
 Buffer.Position := 0;
 Result := true;
end;