                          .-------------------.
                           !Erase !Help file 
                          '-------------------'

Version: 1.1.1 (3 August 2014)

Author: Nat Queen <software@queen.clara.co.uk>

Primary distribution site: http://www.queen.clara.net/pgp/acorn.html


What does it do?
================

!Erase overwrites any data that you want to destroy permanently, using
random data, before deleting the designated files or directories.

When RISC OS 'deletes' a file, the data itself is left intact on the disc
surface until it is (partially) overwritten by some other file; only the
file's entry is actually removed from the directory structure, and disc
editors or 'undelete' utilities can be used to recover the data. !Erase
makes such data recovery virtually impossible.

Who should use !Erase?
======================

!Erase is intended for use in Virtual Acorn systems, as a replacement for
!Nuke by Tony Hopstaken (available from the same URL), which does not work
in such systems. If you use any version of RISC OS on 'native' hardware, it
is preferable to use !Nuke for destroying sensitive data - but please note
that versions of !Nuke earlier than 1.41 do not work in RISC OS 5.

The reason for preferring !Nuke when possible is as follows.

!Nuke is an excellent front end for Sergio Monesi's powerful utility 'nuke',
which makes it possible to overwrite data with various levels of security,
up to the extremely secure Gutmann method with 35 specially designed
successive overwrites. It also allows the free disc space to be securely
overwritten. !Nuke is more versatile and faster than !Erase, but it works
only on native RISC OS hardware.

!Erase has some limitations in comparison with !Nuke. Because its code is
written entirely in BASIC, it is slower than the utility 'nuke'. It also has
fewer options, and in particular no facility for overwriting the free space.
However, for users of Virtual Acorn who wish to destroy sensitive data
permanently, !Erase is still far better than nothing and should give a high
level of security. It overwrites the original data with cryptographically
strong random data, using the module CryptRandom by Theo Markettos.


How to use !Erase
=================

Double-click on the !Erase icon. A directory window for a directory called
'scrap' will open. Any data (files and/or directories) that you place inside
this directory can then be securely overwritten. Simply double-click on the
!Erase icon again, and it will ask for confirmation that you really want to
destroy all the data contained in 'scrap'.

Double-clicking on !Erase has two possible effects. If the directory 'scrap'
is empty, !Erase will simply open its directory window. If 'scrap' contains
any files or directories, it will ask if you want to destroy all the data,
making its recovery impossible. If you enter 'y' or 'Y' in response to this
question, all the files inside 'scrap' (including those in any
subdirectories) will be overwritten with random data before being deleted.
For additional security, their filenames are also overwritten with random
10-character names before deletion.

!Erase gives you the option of a higher level of security for extremely
sensitive data. If, instead of 'y' or 'Y', you enter any number between 2
and 9, all the files and their filenames will be overwritten that number of
times. Of course, if you select a larger number of overwrites, the process
will take correspondingly longer.

If you want to destroy data in some location other than 'scrap', do not
simply 'copy' it into 'scrap' and then 'delete' the original data. This
would allow the original 'deleted' copy to be recovered. Instead, you should
*move* the data to 'scrap' before running !Erase. RISC OS will then merely
change the directory entry of each file, while leaving the data at its
original position on the disc surface, and !Erase can then overwrite it.
This procedure will work only if you are 'moving' the data from the same
disc or filing system.


History
=======

v1.0 - First release (23 May 2004)

v1.1 - Overwrites filenames as well as the actual files; updated CryptRandom

v1.1.1 - Updated CryptRandom


Legal notice
============

!Erase is freeware. The copyright is retained by the author, Nat Queen.  You
may copy and distribute this software freely as long as none of the files
are altered or removed. If you distribute !Erase in any PD library, magazine
cover disc or CD, or on any site on the Internet, please drop a line about
it in my mailbox, so that I can keep you informed about possible future
updates. Any distribution method is allowed, provided that you do not make
any profit from it. This software must not be distributed as part of any
other application without my prior permission.

This software has been thoroughly tested, but no guarantee is given as to
its suitability for any purpose. The author accepts no responsibility for
any data loss, crashes or other undesired effects caused directly or
indirectly by using !Erase.

Thanks to:
==========

Tony Hopstaken, for invaluable suggestions and inspiration.

Theo Markettos, for making his excellent CryptRandom module available to the
RISC OS community.
