Date: Fri, 05 Mar 2004 17:45:00 -0600 (CST)
   From: Mark Jacobson <jacobson@math-cs.cns.uni.edu>
     To: 810-151-05@uni.edu
Subject: Assignment two and Friday, March 5th review...

Hi VB.NET students,

     Since today is 03/05, the following note should have been
        published on 3 by 5 notecards 
                                      in honor of March 5th!  :-)

     Please see the VB.NET class web page at:

     http://www.cns.uni.edu/~jacobson/c151VB.html

     and link to an extensive review of today's class and your
     next programming assignment:

     http://www.cns.uni.edu/~jacobson/030VB/030NetAssign2.htm

     Your next assignment is explained there at the above page.

     It involves reading the contents of an ASCII raw text file and
encrypting each line of the file, and displaying the encrypted lines
in a listbox control.
              1 1 1 1 1
     123456789012345678
     1234567890 PANTHER
                        would be encrypted as:
     48PH   followed by
     37 T   followed by
     260NR  followed by
     159AE                   ---->  48PH37 T260NR159AE  <--- Ciphertext
                                    1234567890 PANTHER  <---  Plaintext

                       1 1 1 1 1 1 1 1 1
     1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8
     1 2 3 4 5 6 7 8 9 0   P A N T H E R
           -       -       -       -       <--- 4, 8, 12, 16th
         *       *       *       *         <--- 3, 7, 11, 15th
       &       &       &       &       &   <--- 2, 6, 10, 14, 18th
     $       $       $       $       $     <--- 1, 5,  9, 13, 17th

    This is called a tranposition cipher technique, since it
    rearranges the letters of the original message to encrypt
    the plaintext into ciphertext.

    The other type of encryption basic approach is called a
    substitution cipher, such as the Caesar cipher, which
    replaces each character with a different character.

    For example:   A is replaced by D, B is replaced by E, etc.

                   If the key for the Caesar cipher is 3, which was
                   the actual key for the very first use of a Caesar
                   cipher.  Secret key 3 means
                                        A becomes D
                                        B becomes E
                                        C becomes F
                                        D becomes G  etc.

                   Caesar cipher method with secret key value of 5
                   would map letter A to F, B to G, C to H, etc.

                   Character( ASCIICodeValue(letter) + 5 )
                        would be the technique to encrypt with key = 5

                   Character( ASCIICodeValue("A") + 5 )
                   Character(           65        + 5 )
                   Character( 70 )
                   "F"

    Your assignment is due on Wednesday, March 10th.

    I will probably not have an in-class quiz on Wednesday, March 10th.
    We can discuss that on Monday in class.

    Mark