Алгоритм 128-битного шифрования (TEA)

Автор: Valts Silaputnins

{ **** UBPFD *********** by delphibase.endimus.com ****
>> Алгоритм 128-битного шифрования (TEA)

Зависимости: system
Автор:       Valts Silaputnins, valts@velns.org
Copyright:   Valts Silaputnins
Дата:        19 августа 2002 г.
***************************************************** }

unit ucrypt;

interface
type
  TEAKey = array[0..3] of cardinal;

//Use 64-bit aligned data size (8,16...) or else some data will be left unencrypted!
procedure TEA_Encode(Input, Output: pointer; size: integer; key: TEAKey);
procedure TEA_Decode(Input, Output: pointer; size: integer; key: TEAKey);

implementation
type
  TEAData = array[0..1] of cardinal;
  PTEAKey = ^TEAKey;
  PTEAData = ^TEAData;

procedure TEA_Cipher(v: PTEAData; var w: PTEAData; k: PTEAKey);
var
  y, z, sum, delta, n: Cardinal;
begin
  y := (v)[0];
  z := (v)[1];
  sum := 0;
  delta := $9E3779B9;
  n := 32;

  while (n > 0) do
  begin
    inc(y, (z shl 4 xor z shr 5) + z xor sum + (k)[sum and 3]);
    inc(sum, delta);
    inc(z, (y shl 4 xor y shr 5) + y xor sum + (k)[sum shr 11 and 3]);
    dec(n);
  end;

  (w)[0] := y;
  (w)[1] := z;
end;

procedure TEA_DeCipher(v: PTEAData; var w: PTEAData; k: PTEAKey);
var
  y, z, sum, delta, n: Cardinal;
begin

  y := v[0];
  z := v[1];
  sum := $0C6EF3720;
  delta := $9E3779B9;
  n := 32;

  while (n > 0) do
  begin
    dec(z, (y shl 4 xor y shr 5) + y xor sum + k[sum shr 11 and 3]);
    dec(sum, delta);
    dec(y, (z shl 4 xor z shr 5) + z xor sum + k[sum and 3]);
    dec(n);
  end;

  w[0] := y;
  w[1] := z;

end;

procedure TEA_EnDec(encode: boolean; Input, Output: pointer; size: integer; key:
  TEAKey);
var
  DataIn, DataOut: TEAData;
  DOut: PTEAData;
  i, sz: integer;
begin
  DOut := @DataOut;
  sz := (size shr 3) shl 3;
  i := 0;
  repeat
    DataIn[0] := Cardinal((pointer(Cardinal(Input) + Cardinal(i)))^);
    DataIn[1] := Cardinal((pointer(Cardinal(Input) + Cardinal(i + 4)))^);
    if encode then
      TEA_Cipher(@DataIn, DOut, @key)
    else
      TEA_DECipher(@DataIn, DOut, @key);
    Cardinal(pointer(Cardinal(Output) + Cardinal(i))^) := DataOut[0];
    Cardinal(pointer(Cardinal(Output) + Cardinal(i + 4))^) := DataOut[1];
    inc(i, 8);
  until i >= sz;

end;

procedure TEA_Encode(Input, Output: pointer; size: integer; key: TEAKey);
begin
  TEA_EnDec(true, Input, Output, size, key);
end;

procedure TEA_Decode(Input, Output: pointer; size: integer; key: TEAKey);
begin
  TEA_EnDec(false, Input, Output, size, key);
end;

end.