I need a routine to securely wipe out a file and have found a couple that
are supposed to do this. But I'm a little concerned about how secure they
are and whether they will really wipe out all traces of the file. The two
routines are listed here and I would appreciate any opinions on which is
better, what possible weaknesses they have, or possible alternatives.
Glenn
-------------
procedure FileWipe(FileName: string, Times: integer);
// Adapted from GX Explorer
var
StringStreamBuffer: TStringStream;
n, intFileSize: integer;
OverwriteChar: char;
begin
for n:=1 to Times do begin
OverwriteChar:=chr(n);
with TFileStream.Create(FileName, fmOpenReadWrite or fmShareExclusive)
do begin
try
intFileSize := Size;
StringStreamBuffer :=
TStringStream.Create(StringOfChar(OverwriteChar, intFileSize));
try
CopyFrom(StringStreamBuffer, intFileSize);
finally
StringStreamBuffer.Free;
end;
finally
Free;
end;
end;
end;
DeleteFile(PChar(FileName));
end;
------------------
procedure ShredFile(const FileName: string; Times: Integer);
// From Jedi JCL code library
const
BUFSIZE = 4096;
ODD_FILL = $C1;
EVEN_FILL = $3E;
var
Fs: TFileStream;
Size: Integer;
N: Integer;
ContentPtr: Pointer;
begin
Size := FileGetSize(FileName);
if Size > 0 then
begin
if Times < 0 then
Times := 2
else
Times := Times * 2;
ContentPtr := nil;
Fs := TFileStream.Create(FileName, fmOpenReadWrite);
try
GetMem(ContentPtr, BUFSIZE);
while Times > 0 do
begin
if Times mod 2 = 0 then
FillMemory(ContentPtr, BUFSIZE, EVEN_FILL)
else
FillMemory(ContentPtr, BUFSIZE, ODD_FILL);
Fs.Seek(0, soFromBeginning);
N := Size div BUFSIZE;
while N > 0 do
begin
Fs.Write(ContentPtr^, BUFSIZE);
Dec(N);
end;
N := Size mod BUFSIZE;
if N > 0 then
Fs.Write(ContentPtr^, N);
FlushFileBuffers(Fs.Handle);
Dec(Times);
end;
finally
if ContentPtr <> nil then
FreeMem(ContentPtr, Size);
Fs.Free;
DeleteFile(FileName);
end;
end
else
DeleteFile(FileName);
end;
