A Unix tool for secure deletion
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README

wipe 0.24 by Berke Durak Wed Nov 02 2016

WHAT IS WIPE ?

"wipe" is a short, nice tool for securely wiping out files from magnetic media.
Purpose: to quickly wipe out traces of your latest dissident activities
(cryptography etc.) when you realise that your local SSP (State Security
Police, aka. NSA, DST, CIA, MIT (Turkish Intelligence Agency), Mossad, ...)
is knocking at your door.

QUICK START

See file "QUICKSTART".

RTFM

Please READ THE MAN PAGE for more detailed information on wipe. Also, if you
haven't done it yet, read Peter Gutmann's article on "Secure Deletion of Data
from Magnetic and Solid-State Memory", included in this directory, which can
also be retrieved from
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html

CHANGES

See the file CHANGES for a short history of wipe. You can get the latest
version of wipe at these addresses:
  http://lambda-diode.com/software/wipe/

COPYING

Wipe is under the GNU Public License (see file COPYING).

PROBLEMS

Wiping is a tricky affair. "wipe" tries to do everything that a portable
user-level program can do to securely erase the given files. However,
there are several limitations:

  1.Since file meta information such as file name, size,
    creation/modification/access dates as well as directory
    structures are filesystem-specific, and as file systems
          tend to have extremely various architectures, there is
    no hope in seeing a uniform interface for accessing
    low-level filesystem data. Therefore a portable program
    must be filesystem-independent. It must thus use
    standard file operations in a way that will make most
    file systems effectively overwrite the desired portions
    of the magnetic media.

  2.Since IDE and SCSI hard disks are driven by their own
    logic, nothing guarantees that the required data is
    written out effectively at the required place, i.e.
    over the old data.

        3.The successfull erasure of off-track data is a function of
          drive temperature, usage history, drive mechanics and
          luck.

Therefore I cannot and will not guarantee you that the files erased with wipe
are unrecoverable. SOME RECENT VERSIONS (0.11, 0.12, 0.13) HAVE SERIOUS BUGS:
I was too lazy to check if wipe was still working as expected after doing
various improvements. It was not. Mea culpa. The current version (0.14)
has been more or less verified, in different wipe modes, on different
files and block devices.

You can use "strace" on wipe to check that it effectively does the announced
writes with different random data. From a software-level, wipe seems to do what
it claims to do, i.e. overwriting, renaming, truncating, etc. Verification at
the hardware-level requires specialised hardware. I don't have hardware.
If anyone has got access to such hardware and is willing to check the
effectiveness of wipe (and other secure deletion tools) PLEASE INFORM THE
PUBLIC ABOUT IT.

Verifications made on an Ext2 file system mounted through loopback shows
that wipe 0.14 correctly erases the data blocks of files. However, file name
wiping did not work as well as expected: plain filenames were still
discernable at the block level after wiping a large directory tree.
But filling the filesystem with a maximum size file and wiping it
(as a crude but portable way to wipe out free blocks) erased the
remaining plain filenames.

There will be problems with files having "holes" in them; as wipe will
try to completely overwrite those files with random data, the holes
will get filled, possibly exceeding available disk space.

Briefly: you can reasonably expect that the DATA contained in your files
is EFFECTIVELY WIPED. However on complex file systems like Ext2
it is likely that FILE META-INFORMATION is NOT securely erased, or
even not overwritten at all.

RECOMMANDATIONS FOR MAXIMUM SAFETY

For maximum safety, use an encrypted file system.
Use wipe to clean whole partitions. For example, if I had guilty
stuff on /dev/hda3, assuming that /dev/hda3 is less than, say 70% full,
I would first mount /dev/hda3 on /mount, then do
  wipe -cfrsF /mount/
to wipe the contents of the data files using 34 passes, then
  wipe -kqZ -Q 1 /dev/hda3
to erase file meta-information. However if /dev/hda3 is more
than 70% full, it might be quicker to erase the whole hard disk
using 34 passes:
  wipe -kZ /dev/hda3
If you don't have to hide that you have guilty stuff but just want
to be sure that someone else won't get at the CONTENTS of that guilty
stuff, or in other words if you don't care about wiping file names,
sizes etc. but just want to wipe out file contents, simply do
  wipe -cfrZF /mount/.

And, last but not least, think of TEMPEST monitoring. I don't know
how feasible it is to remotely eavesdrop your computer's internal
bus or your IDE ribbon but using the "-s" (silent) option will prevent
wipe from outputting to your monitor the names of all the files it
erases. Eavesdropping your CRT is much easier for amateurs as well
as for professionals.

REQUIREMENTS

wipe used to require Linux kernel 2.0.x or newer, in order to use the O_SYNC
bit, and the /dev/random device. Since version 0.10, it no longer expressely
requires O_SYNC, uses strong PRNGs and can gather the required seeds from
different sources, including /dev/random-like devices, by hashing the output of
a user-defined command or, in the worst case, by hashing its PID, the local
date/time and its environment variables.

Thanks to Chris L. Mason <cmason@unixzone.com> who initially motivated me to
make wipe portable and helped me with compilation tips, bug reports,
suggestions and patches. He maintains a site with reviews on UNIX software at
http://www.unixzone.com

THANKS

Many thanks to the following people who sent in bug reports, compilation tips,
and even whole patches ! In alphabetical order, hoping to not forget anyone,
they are:

  Alexey Marinichev
  Chris L. Mason
  Jason Axley
  Erik Vogan, 64-bit offset fix
  Michael S. Rhee
  Paul H. Hargrove
  Peter Miller, for contributing an ETA patch
  Thomas Schoepf
  Joao Eriberto Mota Filho

INSTALLATION

To compile wipe, type "make" to get a list of supported unices. If your
operating system appears in the list, type "make <your operating system>";
otherwise try "make generic". If this does not work, you'll have to
hand-edit the Makefile: please mail me about your results.

You can then copy the "wipe" executable in /usr/local/bin/ or in ~/bin if you
wish. Install the man page in /usr/local/man/man1/, or use "man -l wipe.1" to
read the manual page from wipe's directory.

On systems lacking a /dev/random-like device, the shell script "randompipe.sh"
can be used with the -R and -S options or the WIPE_SEEDPIPE environment
variable. For more info, see the man page.

OTHER WIPE IMPLEMENTATIONS

There are several file-wiping tools available for Windows. There are two other
ones I know for Linux: Calvin Clark's wipe 1.0beta, and Tom Viers' wipe
v0.55beta3. These have exactly the same semantics as mine, i.e. their aim is to
overwrite files with data in order to prevent recovery of their contents. Tom
Viers' wipe is very similar to mine and is also based on Peter Gutmann's
article.  However, Calvin's wipe does simply write zeroes out on the file,
which is not secure at all (RTF article !). There is also Van Hauser's srm
(secure remove) available at http://r3wt.base.org, and which uses /dev/urandom
as a PRNG.

AUTHOR

I can be reached at <berke@lambda-diode.com>.  Send bug reports, ideas for
improvement, compilation problems and other comments to this address.