Ceaser Cipher

Category:

String Manipulation

Type:

Applications

Difficulty:

Beginning

Author:

Anonymous

Version Compatibility: Visual Basic 6

More information:

This is a simple form of encryption/decryption also called a shift cipher

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
' (None)

Code:

Private Sub Command1_Click()
'*********YOU WILL NEED 3 TXTBOXES NAMED:(txtcipher, txtanswer, txtnum), _
'3 LABELS, AND 3 CMD BUTTONS THE LABELS AND CMD BUTTONS USE THE DEFAULT _
'NAMES***************
Dim size As Integer
Dim letter As Variant
Dim encrypt As String
Dim char As String
Dim codeasc As String
Dim ans() As String
Dim count As Variant
Dim box As Variant

txtanswer.Visible = False

'calls msgbox for useless rotation
If txtnum.Text = "26" Then
    MsgBox " A rotation of 26 gives you no rotation at all. Considering that there are 26 letters in the alphabet.", vbOKOnly, "ERROR"
    txtanswer.Text = "This is a wothless rotation" & "... " & UCase(txtcipher.Text)
    txtanswer.Visible = True
Exit Sub
End If
If txtnum.Text = "" And txtcipher.Text = "" Then
    MsgBox "Input some info.", vbInformation + vbOKOnly, "Missing Info."
Exit Sub
End If

'if the number of rotations box is an empty string alert user
If txtnum.Text = "" Then
    MsgBox "Input a number of rotations.", vbInformation + vbOKOnly, "Missing Info."
Exit Sub
End If

'alert user that 26 is the highest rotation number
If Val(txtnum.Text) > 26 Then
    MsgBox " Sorry can only rotate by the amount of letters in the alphabet.", vbInformation + vbOKOnly, "ERROR"
    txtnum.SetFocus  'puts focus back to rotations box for correction
    txtnum.Text = ""  'clears rotations box for correction
    Exit Sub  'if this is true stop program for correction and retry
End If
    
size = Len(txtcipher.Text) 'size = amount of letters in the typed in word

encrypt = "" 'encrypt is a empty string right now

ReDim ans(size) 'makes the size of the array the same as the number of letters in the word entered

box = Val(txtnum.Text) 'setting a variable to the rotations text box

For letter = 1 To size
    char = Mid(txtcipher.Text, letter, 1) 'checks each letter 1 by 1
    codeasc = Asc(char) 'gets the ascii code for each letter
    encrypt = codeasc + box 'variable that figures out what letter to go to depending on the following conditionals
   
If encrypt > 122 Then ' if the ascii code goes higher than 122...
    encrypt = (encrypt - Asc("z") + Asc("`")) ' take the ascii code for "z" 122 and take away the ascii code for the letter it is checking and add 96 "`" ascii number ( 97 ia ascii for "a")
End If

If encrypt < 97 Then 'for spaces that are typed in if under ascii 97 "a" then it must be a "space" ascii 32
    encrypt = Asc(" ")
End If

count = Chr(encrypt)
   ans(size) = count

txtanswer.Text = txtanswer.Text + ans(size)

Next letter

txtanswer.Visible = True

txtcipher.Text = UCase(txtcipher.Text)

End Sub

Private Sub Command2_Click()
    
    'when this button is clicked it will clear the 3 text boxes and set focus back to txtcipher
    txtcipher.Text = ""
    txtcipher.SetFocus
    txtnum.Text = ""
    txtanswer.Text = ""
    txtanswer.Visible = False
End Sub

Private Sub Command3_Click()
'ends the program
    End
End Sub

Private Sub Form_Activate()
txtcipher.SetFocus
txtanswer.Visible = False 'makes txt box invisible
End Sub