The Datafile PD-CD 5/DATAFILE_PDCD5.iso/utilities/s/suremail/UserGuide

Text File | 1994-02-06 | 15KB | 262 lines

CipherEngine v0.66 User Guide (ShareWare release)
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1.1 License
===========
You are licensed to use this application in an unregistered state for
a period of 30 days.  After this time you must either delete all copies
of the software in your posession or register with the author.
You may pass unregistered versions of the software to any other person
on any media even after this period of 30 days (ie if you're a PD
library) provided that you are not using the software yourself.
You cannot use the modules in your own programs unless you are
registered, as the registration fee includes a distribution license.
By breaking the terms of this license you are breaking the law.

Registration costs £5.00.  For this fiver, you get a registration pack
comprising all the source code, a few examples, a manual on disc
detailing all the SWIs in the module, and some other goodies.
You also get free support and you get listened to when you complain!
(you don't if you're unregistered unless you've got something very
good to say!! [I jest -: ??]).  In short, you get a fair bit more than
the single application that you got with this release!  All discs are
high quality 3M floppies, formatted to 800K standard (E-format).
There are some programming examples in the documentation.  All this
ammounts to a very substantial suite of programs for your money.

To register: Send a cheque/postal order for £5.00 made payable to
Mr Seery in a sealed envelope, together with your order form (see below).
You will receive, by first class post, your registered version within
fourteen days, except in exceptional circumstances, although I hope to
turn around orders more quickly than this.

Ordering is made simple by my wonderful ordering program (!).  Somewhere
on this disc you should find an application !Order.  Load it and
double-click on its icon to open up two windows.  Enter your name and
address in the Customer Ordering Details window and toggle the mainshots
button if necessary.  Then select OK and move to the Customer Program
Details window.  This window provides details about the piece of software
under consideration. Select the appropriate piece of software by clicking
menu over the arrow next to the 'Program:' slot and choosing the right
item.  The window displays the program name, cost, and details.
Click 'OK' to order this piece of software.  Quit the program when you've
finished (it tells you how much you owe) and then bung it on a disc
and send it to me.  You get your order processed more quickly if you
use this method, but if you can't find the program then just write a
note specifying which program you want and the total cost.
REMEMBER: When passing the application on to someone else, pass on
a version with no pieces of software marked as ordered.  This entails
copying the program to another disc before using it as the details are
saved inside its directory.

Right, legal stuff over with now:

1.2 Introduction
================
CipherEngine is a module providing encryption and compression utilities
for Acorn Risc OS computers.  It is, to the best of my knowledge, the
only encryption utility providing archiving and encryption suitable
for EMail, as it calculates digital signatures for all files archived
and checks against tampering as they are de-archived.  Unless you are
a programmer you will probably be using the !SureMail application to
create encoded versions of your data.  Programmers should refer to
the Reference Manual supplied with the registered version for details
of the SWIs supported by the module.

PLEASE NOTE: YOU MUST HAVE THE 'SQUASH' MODULE FROM RISC OS 3 LOADED
TO USE THIS APPLICATION! !SureMail works on Risc OS 2 provided that
Squash is present.

Calling all programmers!

Remember that CipherEngine doesn't necessarily have to be used for
encryption.  It includes SWIs for squashing whole directories and single
files, and a variety of other useful bits and bobs.  An example of the
non-cryptographic use of the module is my own trashcan, !TrashFS, which
squashes all trashed files using a CipherEngine SWI.

2.1 !SureMail - User Guide
==========================
Load !SureMail by double-clicking on its icon in a filer viewer.
We are going to simulate a typical EMail session (remember that you don't
have to use !SureMail for EMail - it can be used just for encoding
sensitive data or anything else, for that matter) so you will need a
file or three to test.  If you haven't got anything, use this user guide
as an example.

Click on its icon on the icon bar and a large window will open, but it is
resizable if your display is cluttered.  The basic idea is to "pack" several
files into one file, called an "envelope".  This is analagous to putting
several letters into one real, paper, envelope.  The letters are then
"signed" (using what is known as a Digital Signature) and the "envelope"
is "sealed" (encryption).  You can probably tell that this sort of encryption
is tailored towards EMail, but there is another sort of file (an SEA)
that SureMail produces which is not - see later.
Anyway, fill in the 'To', 'CC', 'Subject', and 'From' fields.  You will
then need to chose two keys.  One is a single letter key - the ID key -
which is used for doubly encoding the details fields that you have just
filled in.  The second - the Envelope Key - is used for encoding the
entire envelope, and this can be up to 16 characters long.  As an aside
into encryption arithmetic, this gives 2^128 combinations (just take my
word for it!) which means that it would take about a trillion years
for an Acorn computer to crack by "brute force" (trying every single
combination until one is found that works).  Longer keys are better than
short ones, but are harder to remember.  You must specify case, spacing,
in fact everything, perfectly.  When you have set this up to your
satisfaction - be very careful entering keys, as they show up as asterisks
to minimise the risk of someone reading it over your shoulder - change
the filename in the writable icon in the 'Save as:' box, and drag the
file icon to a directory viewer.  You can now start adding files, as this
initial setup window disappears, to be replaced by one with a big arrow
in it.  Drag files - or directories - to this arrow to add them to the
envelope.  They are compressed en route, but not encrypted, to minimise
the final encryption time.  When you have finished, click on the OK
button, and the encryption process will start.  At this point, you may
receive a message of the form: 'File size not divisable by 8.  The last <x>
bytes will not be encrypted' where <x> is a number between 1 and 7.  This
means that the encryption algorithm is unable to encrypt the entire file,
and will ignore the last <x> bytes.  This is not a problem, however,
as it would be very difficult to ascertain either the key or the file's
contents from the last - at a maximum - 7 bytes!!  When the encryption
process has finished, another message will pop up telling you how many
centi-seconds (hundredths of a second) it took to encode a file.  The
encoding process is very quick and even for 100k plus files on a floppy
it is likely to be well under 10 seconds.  On a fast ARM3 with a RAM
or hard disc you are unlikely to notice any delay!

At this point the envelope is ready to be sent off either on disc or
via the phone line.  Errors introduced during the transmission of
data will be picked up on when an attempt is made to dearchive the
envelope, which is described below.

To dearchive the envelope, either double-click it (with or without !SureMail
being loaded) or drag it to !SureMail's icon on the icon bar.  A window
will open requesting the passwords and you must type this in EXACTLY as
they were specified when the envelope was created.  The envelope will then
be decrypted.  If you receive the message 'Not a packed envelope' then
you have typed the passwords in wrongly, or the file has suffered so much
damage in transit that it is unreadable to the scanning algorithm.  After
it has been decoded the envelope is useless, so I suggest that you make a
copy of it first and then try decoding the copy.  You will lose all th