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https://github.com/berke/wipe

A Unix tool for secure deletion
https://github.com/berke/wipe

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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  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 ";

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 .  Send bug reports, ideas for

improvement, compilation problems and other comments to this address.