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                       ^3P R O G R A M   P A R L O U R
                 
                 ^2The definitive guide to AMOS programming

                               ^1by Ben Ashley

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^7 This part of `Totally Amos', is a sort of...well, a guide, hintbook,
^7listing book, etc.  And over the months, I`ll be uncovering routines,
^7and  giving a helping hand to anyone who needs it.  I remember when I
^7first  got  AMOS.  Wow, did it look daunting or what?  Even with such
^7good  helplines around.  Still, I`ve got to grips with it, and here I
^7am now, speaking to you.

^5 This issue, I`m going to be looking at Password Protection.  It is a
^5scheme, that I`ve been planning for a couple of months now.  I have a
^5few  BETA tests, but I have yet to get round to writing and compiling
^5a  full  blown protection kit.  So, without further ado, I`m going to
^5set off on some theory work.

^7 However  good  the  protection,  you  can  bet  your life, it can be
^7cracked.  So rather than set sail on the waters of impossibility, I`m
^7going  to  embark  on the project of the lesser-technical minded.  If
^7you  couldn't  make  head  nor  tail  of that last sentence, what I`m
^7trying  to  say  is,  my  Password  Project is to protect your disks,
^7against  the people who are NOT hardened crackers.  Problem is, a lot
^7of  people  are reading this article and finding out how certain ones
^7work.   Change  them  if  you  wish, the idea is there, and it`s only
^7supposed  to  keep  fellow  companions and family out of your private
^7life.

^2THE PASSWORD PROGRAMS

^5 There will only really be 2 main programs you`ll need to write.  One
^5which  installs  passwords  onto  disks, and another compiled program
^5which can be put in a startup-sequence, e.t.c.

^2THE PASSWORD ITSELF

^7 When  asking for a password to be put on the disk, we`ll say that it
^7should be held in string P$.  O.k, to save this password, it`ll go in
^7an  ASCII  file.  GREAT!  I hear you cry, people can just look at it!
^7So here comes the interesting part.  The encryption.  You could use a
^7routine like the following:

^6 L=Len(P$)
^6 For F=1 To L
^6    Mid$(P$,F,1)=Chr$(Asc(Mid$(P$,F,1))+5)
^6 Next F

^5 This  should  change the values of the Ascii characters, so it looks
^5like a load of junk.  And then you`d save it as a sequential file.

^7 Now, in the PASSWORD PROTECTION PROGRAM, to Decrypt the password all
^7you have to do is......

^6 L=Len(P$)
^6 For F=1 To L
^6    Mid$(P$,F,1)=Chr$(Asc(Mid$(P$,F,1))-5)
^6 Next F

^7 This should get the password back to it`s original state.

^7 So, a fully blown routine could look something like:

^6 Input "Please enter the New Password:";P$
^6 L=Len(P$)
^6 For F=1 To L
^6    Mid$(P$,F,1)=Chr$(Asc(Mid$(P$,F,1))+5)
^6 Next F
^6 Open Out 1,"Df0:File.X"
^6 Print #1,P$
^6 Close 1
^6 Edit

^7And the checking program......

^6 Open In 1,"Df0:File.X"
^6 Input #1,P$
^6 Close 1
^6 For F=1 To L
^6    Mid$(P$,F,1)=Chr$(Asc(Mid$(P$,F,1))-5)
^6 Next F
^6 Input "Please enter the Password:";PASS$
^6 If PASS$=P$
^6    End
^6 End If 
^6 Do
^6   Curs Off
^6   Amos To Front
^6 Loop


^7 Of course, you`ll have to add, a good screen ( ie:  2 colour, hi-res
^7), and when you`ve made sure you`ve got it right.  Add BREAK OFF.  In
^7the  Password Program I wrote, I put the command Amos To Front in the
^7loop.

^5 This  meant,  if  any  person  who had failed to put the password in
^5correctly,  and  tried to switch screens using AMIGA-A, could not, as
^5the AMOS screen would always be brought to the front.
    

^7 So  what  have  I  included as source?  Well, to give you an idea of
^7what  I`m  talking  about,  I`ve  provided  you with THREE, yes THREE
^7programs.  These are:

^2                         Password-Installer.AMOS
^2                         Password-Protection.AMOS
^2                         Password-Cracker.AMOS

^7 The  first two are self explanatory.  The first is the one you place
^7a   password   in,   the   second   gets   compiled   and  put  in  a
^7startup-sequence,  and  the  third.....  Just in case you forget your
^7password, this one cracks passwords.

^2 Well,  Tally-Ho,  and enjoy your Password Programming.  See you next
^2issue...  BYE!

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