                        .-----------------------.
                         !Mail-Lock !Help file 
                        '-----------------------'

Version: 1.5.1a (3 August 2014)

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

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

*** NOTE *** This version does not work in Virtual Acorn systems. If you are
using such systems, you should get version 1.5b from the same URL. See the
section "Why is there a separate version..." below for an explanation.


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

!Mail-Lock enables you to encrypt specified mail folders or to retrieve
them, in a very simple manner, if you use !Marcel in the ANT Internet Suite.

!Mail-Lock can encrypt many different mail folders (not necessarily for the
same local user), each with its own passphrase. The mail folders for which
encryption is enabled are referred to below as 'secure mail folders'.

Many commercial programs claim to provide 'virtually unbreakable' encryption
without revealing the encryption method. As Phil Zimmermann, creator of PGP,
said in his PGP manual, "Beware of snake oil." The encryption system in
!Mail-Lock relies solely on the renowned Blowfish cipher, whose source code
is freely available and has been scrutinised by numerous experts. Moreover,
this software is free.

As an extra security measure, !Mail-Lock makes use of Sergio Monesi's
powerful utility 'nuke' to erase all traces of the original files from the
disc after they are encrypted, making it impossible for snoopers to recover
them. When a file is 'deleted' by RISC OS, only its entry in the directory
structure is removed, but all the data remain on the disc surface and can
easily be recovered by means of a disc editor or an 'undelete' utility;
'nuke' prevents such data recovery by overwriting the data with 'military'
security.


How to get started
==================

Before you can run !Mail-Lock, you must connect to the mail server in
!Marcel. When you connect as a particular local user, !Mail-Lock will
recognise only the mail folders for that particular local user.

If you close !Marcel, !Mail-Lock will continue to recognise the mail folders
of the most recent local user. It is therefore recommended that you always
connect to the mail server in !Marcel before using !Mail-Lock.

Having connected as a particular local user, the next step is to decide
which of your mail folders you will want to encrypt. These will be your
'secure mail folders'. Each secure mail folder can be encrypted
independently, with its own passphrase. The encrypted files will be
inaccessible to anyone who does not know the correct passphrase. Of course,
if you wish, you may use the same passphrase for different mail folders.

When you double-click on !Mail-Lock, a directory window will open. In it,
you will see an application !Folders. This is a mail-folder manager, used to
create secure mail folders (i.e. to enable encryption) or to change secure
mail folders back to normal ones (for which encryption is not enabled).

If you double-click on !Folders, another directory window will open, in
which you will see the two applications !Secure and !Normal, used to create
secure mail folders or to change secure mail folders back to ordinary ones.
To use these applications, simply double-click on one of them and follow the
on-screen instructions. Note that !Normal will not do anything if a mail
folder is encrypted; it is necessary to decrypt it first. The utility
!Normal not only disables encryption, but also deletes various directories
associated with a secure mail folder.

It is important to understand that the utilities !Secure and !Normal do not
encrypt or decrypt anything. They simply enable or disable encryption of a
specified mail folder, and, at the same time, they create or delete certain
directories associated with a secure mail folder. The use of these utilities
has absolutely no effect on your !Marcel mail folders themselves.

Do not attempt to create or remove secure mail folders by hand. It is much
simpler and safer to use !Secure or !Normal.

Apart from !Folders, the directory window that opens when you double-click
on !Mail-Lock also contains two other utilities, !LockMail and !OpenMail, as
well as a directory 'Encrypted'. The directory 'Encrypted' (which you need
not normally open) will contain all your encrypted mail folders. The
utilities !LockMail and !OpenMail are described below.

The directory 'Encrypted' will contain subdirectories to hold the encrypted
versions of each of your secure mail folders, but they will remain present
as empty subdirectories when those folders are not encrypted, as long as
those folders are declared as 'secure mail folders'. Therefore the easiest
way to check the full list of secure mail folders at any time, whether or
not they are encrypted, is to open the directory 'Encrypted' and look at its
subdirectories.


Encryption
==========

To encrypt your mail, double-click on the !LockMail icon. The program will
first ask which secure mail folder you want to encrypt, and will then ask
for a passphrase. It is essential that you remember this passphrase. Bear in
mind that the passphrase is case-sensitive. If you forget the passphrase
with which you encrypt your mail, there will be absolutely no way to recover
the mail (unless you used a weak passphrase!).

After entering your passphrase twice for confirmation, the original mail
folder will be securely wiped and replaced by one containing a single 'mail'
message from !Mail-Lock telling you that the folder has been encrypted. The
original mail messages will be stored in encrypted form in a single file
inside the corresponding subdirectory of the directory 'Encrypted'.

When a mail folder is encrypted, the corresponding overview file (if one
exists) is securely wiped in addition to the original mail folder itself.
This makes it impossible for snoopers to extract any information about what
mail messages were in that folder.


Decryption
==========

To decrypt your mail, double-click on the !OpenMail icon. You will first be
asked which secure mail folder you want to recover, and then for the
passphrase that you used to encrypt it. If you enter the correct passphrase,
the original mail folder will reappear. If you enter the wrong passphrase by
mistake, you may try again, until you get it right.

If you want your mail to remain secure, don't forget to use !LockMail again
when you finish your session!

In the very unlikely event that any of your encrypted files are accidentally
deleted or corrupted, you will find a backup copy inside the directory
!Mail-Lock.MlockDir.!LockMail.Backups, which can be copied back to its
normal position inside 'Encrypted', from which it can be recovered by using
!OpenMail. This backup is created automatically every time you encrypt a
mail folder.


Security considerations and !Q-Lock
===================================

When you receive confidential messages by mail, you may want to store them
in some place other than in a secure mail folder. Perhaps you need to store
other sensitive data too. For that purpose, it is recommended that you use
!Mail-Lock's sister program !Q-Lock, available from the same download site
as !Mail-Lock. These two programs work in the same way, and they have a very
similar look and feel.

!Q-Lock can also be used for permanently destroying confidential files or
directories, so that they cannot be recovered from the disc. The documents
in !Q-Lock explain how to do this.

The passphrase is usually the weakest link in an encryption program, being
susceptible to a 'dictionary attack' or 'brute-force attack'. Some tips for
constructing a strong passphrase can be found in !Q-Lock's documents.


'True Military' nuking
======================

For users who need to protect sensitive data against the most sophisticated
types of attacks, there is a special 'True Military' option, which is
considerably slower but much more secure than the default 'military'
security level.  This does not alter the method of encryption in any way,
but it gives extra confidence that any files which might reveal sensitive
information are securely wiped from the disc, with no possibility of
recovery.  This option is described in detail in the accompanying file
'ExpertHelp'.


Why is there a separate version for Virtual Acorn systems?
==========================================================

The original version of this software contained the very powerful utility
'nuke', which does not work in those systems. Therefore a separate version
was created by replacing 'nuke' with a BASIC program to carry out a similar
function. However, this BASIC program is somewhat slower and more limited in
its security features than the original 'nuke'. !Mail-Lock 1.5a retains the
original and more powerful 'nuke'.


History
=======

v1.00 - First release (1 February 1999)

v1.2 - Added !Folders; support for multiple local users; improved security
       (15 June 1999)

v1.3 - Fully compatible with RISC OS 4; option for 'True Military' nuking
       (6 September 1999)

v1.4(a,b) - Replaced IDEA and MD5 by the more secure Blowfish and SHA-1.
            (22 September 2004)

   [v1.4a is for RISC OS 3 or 4; v1.4b is for RISC OS 5 or Virtual Acorn]
   [v1.4b contains a new 'erase' procedure instead of 'nuke']

v1.5(a,b) - Updated 'nuke' in v1.5a; updated CryptRandom module in v1.5b
            (5 January 2009)

  [v1.5a is for use on 'native' hardware]
  [v1.5b is for Virtual Acorn systems]

v1.5.1(a,b) - Updated CryptRandom (in 'b') and SHA1


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

!Mail-Lock 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 !Mail-Lock 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 !Mail-Lock.

!Mail-Lock contains utilities by other authors, who retain the copyright to
their respective utilities.


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

Tony Hopstaken, for invaluable help, suggestions, and inspiration, all of
which made this a much better program.

Gareth McCaughan, for porting the Blowfish cipher to RISC OS and for making
it freely available.

Stefan Bellon, for recompiling the Blowfish module to make it compatible
with 32-bit systems.

Theo Markettos, for permission to include his SHA1 module in this software.

Sergio Monesi, for permission to include his 'nuke' utility in this
software, and for helpful advice.

Jenny Queen, for help in designing the !Mail-Lock icon.