SRM(1)							      General Commands Manual							    SRM(1)

NAME

       srm - secure remove (secure_deletion toolkit)

SYNOPSIS

       srm [-d] [-f] [-l] [-l] [-r] [-v] [-z] files

DESCRIPTION

       srm  is	designed to delete data on mediums in a secure manner which can not be recovered by thiefs, law enforcement or other threats.  The
       wipe algorythm is based on the paper "Secure Deletion of Data from Magnetic and Solid-State Memory" presented at the  6th  Usenix  Security
       Symposium by Peter Gutmann, one of the leading civilian cryptographers.

       The secure data deletion process of srm goes like this:

       *      1 pass with 0xff

       *      5 random passes. /dev/urandom is used for a secure RNG if available.

       *      27 passes with special values defined by Peter Gutmann.

       *      5 random passes. /dev/urandom is used for a secure RNG if available.

       *      Rename the file to a random value

       *      Truncate the file

       As an additional measure of security, the file is opened in O_SYNC mode and after each pass an fsync() call is done.  srm writes 32k blocks
       for the purpose of speed, filling buffers of disk caches to force them to flush and overwriting old data which belonged to the file.

COMMANDLINE OPTIONS

       -d     ignore the two special dot files . and .. on the commandline. (so you can execute it like "srm -d .* *")

       -f     fast (and insecure mode): no /dev/urandom, no synchronize mode.

       -l     lessens the security. Only two passes are written: one mode with 0xff and a final mode random values.

       -l     -l for a second time lessons the security even more: only one random pass is written.

       -r     recursive mode, deletes all subdirectories.

       -v     verbose mode

       -z     wipes the last write with zeros instead of random data

LIMITATIONS

       NFS    Beware of NFS. You can't ensure you really completely wiped your data from the remote disks.

       Raid   Raid Systems use stripped disks and have got large caches. It's hard to wipe them.

       swap, /tmp, etc.
	      Some of your data might have a temporary (deleted) copy  somewhere  on  the  disk.  You  should  use  sfill  which  comes  with  the
	      secure_deletion  package	to ensure to wipe also the free diskspace. However, If already a small file aquired a block with your pre-
	      cious data, no tool known to me can help you here. For a secure deletion of the swap space sswap is available.

BUGS

       No bugs. There was never a bug in the secure_deletion package (in contrast to my other tools, whew, good luck ;-)  Send	me  any  that  you
       find.  Patches are nice too :)

AUTHOR

       van Hauser / THC <vh@thc.org>

DISTRIBUTION

       The newest version of the secure_deletion package can be obtained from http://www.thc.org

       srm and the secure_deletion package is (C) 1997-2003 by van Hauser / THC (vh@thc.org)

       This  program  is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
       the Free Software Foundation; Version 2.

       This program is distributed in the hope that it will be useful, but WITHOUT ANY	WARRANTY;  without  even  the  implied	warranty  of  MER-
       CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

SEE ALSO

       sfill (1), sswap (1), sdmem (1)

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