vb5 - simple & limited encryption/decryption function

This function will encrypt/decrypt a string up to 30 characters. It will only encrypt uppercase letters A-Z, numbers 0-9 and the following symbols: [ ] * space ' #. The minimum length of the string must be 8 characters. It's very redundant code but it does its intended function and it's easy to understand what is going on in the code. This code could be built on by adding lowercase letters a-z and other symbols.

Also, after encrypting the text, it will scramble the first 4 characters & the last 4 characters.

vb Code:

Public Function subEncrypt(textToEncrypt As String)
 
'sub to encrypt letters
 
Dim a(1 To 30) As String, encryptedText As String, scrambledText As String
Dim textLength As Integer, x As Integer, y As Integer
Dim tmp1 As String, tmp2 As String, tmp3 As String, tmp4 As String, tmp5 As String, tmp6 As String, tmp7 As String, tmp8 As String
 
'assign textlength length of texttoencrypt
textLength = Len(textToEncrypt)
 
'for/next to go through each letter in texttoencrypt
For x = 1 To textLength
    a(x) = Mid(textToEncrypt, x, 1)
 
    Select Case a(x)
        Case Is = "A"
            a(x) = "-"
        Case Is = "B"
            a(x) = ")"
        Case Is = "C"
            a(x) = "?"
        Case Is = "D"
            a(x) = "#"
        Case Is = "E"
            a(x) = "<"
        Case Is = "F"
            a(x) = "6"
        Case Is = "G"
            a(x) = "b"
        Case Is = "H"
            a(x) = "Z"
        Case Is = "I"
            a(x) = "="
        Case Is = "J"
            a(x) = "8"
        Case Is = "K"
            a(x) = "p"
        Case Is = "L"
            a(x) = "a"
        Case Is = "M"
            a(x) = "9"
        Case Is = "N"
            a(x) = ">"
        Case Is = "O"
            a(x) = "}"
        Case Is = "P"
            a(x) = "2"
        Case Is = "Q"
            a(x) = "4"
        Case Is = "R"
            a(x) = "1"
        Case Is = "S"
            a(x) = "v"
        Case Is = "T"
            a(x) = "."
        Case Is = "U"
            a(x) = "3"
        Case Is = "V"
            a(x) = "l"
        Case Is = "W"
            a(x) = "B"
        Case Is = "X"
            a(x) = "\"
        Case Is = "Y"
            a(x) = "T"
        Case Is = "Z"
            a(x) = "h"
        Case Is = "0"
            a(x) = "e"
        Case Is = "1"
            a(x) = ";"
        Case Is = "2"
            a(x) = "k"
        Case Is = "3"
            a(x) = "!"
        Case Is = "4"
            a(x) = "$"
        Case Is = "5"
            a(x) = "@"
        Case Is = "6"
            a(x) = "/"
        Case Is = "7"
            a(x) = "+"
        Case Is = "8"
            a(x) = "G"
        Case Is = "9"
            a(x) = ":"
        Case Is = "["
            a(x) = "%"
        Case Is = "]"
            a(x) = "("
        Case Is = "*"
            a(x) = "^"
        Case Is = " "
            a(x) = "_"
        Case Is = "'"
            a(x) = "S"
        Case Is = "#"
            a(x) = "x"
    End Select
    
    'put encrypted letters into encryptedtext
    encryptedText = encryptedText & a(x)
Next x
 
'assign first 4 letters & last 4 letters
tmp1 = a(1)
tmp2 = a(2)
tmp3 = a(3)
tmp4 = a(4)
tmp5 = a(textLength - 1)
tmp6 = a(textLength - 2)
tmp7 = a(textLength - 3)
tmp8 = a(textLength)
 
'scramble (switch) letters
a(1) = tmp3
a(2) = tmp6
a(3) = tmp1
a(4) = tmp8
a(textLength - 1) = tmp7
a(textLength - 2) = tmp2
a(textLength - 3) = tmp5
a(textLength) = tmp4
 
'put scrambled letters back into text
For y = 1 To textLength
    scrambledText = scrambledText & a(y)
Next y
 
'make sure function returns final encrypted & scrambled text
subEncrypt = scrambledText
 
End Function
 
'/////////////////////////
 
Public Function subDecrypt(textToDecrypt As String)
 
'sub to decrypt text file
 
Dim a(1 To 30) As String, decryptedText As String, unscrambledText As String
Dim textLength As Integer, x As Integer, y As Integer
Dim tmp1 As String, tmp2 As String, tmp3 As String, tmp4 As String, tmp5 As String, tmp6 As String, tmp7 As String, tmp8 As String
 
'assign textlength length of texttodecrypt
textLength = Len(textToDecrypt)
 
'for/next to go through each letter in texttodecrypt
For x = 1 To textLength
    a(x) = Mid(textToDecrypt, x, 1)
 
'decrypt letters
    Select Case a(x)
        Case Is = "-"
            a(x) = "A"
        Case Is = ")"
            a(x) = "B"
        Case Is = "?"
            a(x) = "C"
        Case Is = "#"
            a(x) = "D"
        Case Is = "<"
            a(x) = "E"
        Case Is = "6"
            a(x) = "F"
        Case Is = "b"
            a(x) = "G"
        Case Is = "Z"
            a(x) = "H"
        Case Is = "="
            a(x) = "I"
        Case Is = "8"
            a(x) = "J"
        Case Is = "p"
            a(x) = "K"
        Case Is = "a"
            a(x) = "L"
        Case Is = "9"
            a(x) = "M"
        Case Is = ">"
            a(x) = "N"
        Case Is = "}"
            a(x) = "O"
        Case Is = "2"
            a(x) = "P"
        Case Is = "4"
            a(x) = "Q"
        Case Is = "1"
            a(x) = "R"
        Case Is = "v"
            a(x) = "S"
        Case Is = "."
            a(x) = "T"
        Case Is = "3"
            a(x) = "U"
        Case Is = "l"
            a(x) = "V"
        Case Is = "B"
            a(x) = "W"
        Case Is = "\"
            a(x) = "X"
        Case Is = "T"
            a(x) = "Y"
        Case Is = "h"
            a(x) = "Z"
        Case Is = "e"
            a(x) = "0"
        Case Is = ";"
            a(x) = "1"
        Case Is = "k"
            a(x) = "2"
        Case Is = "!"
            a(x) = "3"
        Case Is = "$"
            a(x) = "4"
        Case Is = "@"
            a(x) = "5"
        Case Is = "/"
            a(x) = "6"
        Case Is = "+"
            a(x) = "7"
        Case Is = "G"
            a(x) = "8"
        Case Is = ":"
            a(x) = "9"
        Case Is = "%"
            a(x) = "["
        Case Is = "("
            a(x) = "]"
        Case Is = "^"
            a(x) = "*"
        Case Is = "_"
            a(x) = " "
        Case Is = "S"
            a(x) = "'"
        Case Is = "x"
            a(x) = "#"
    End Select
 
    'put decrypted letters in decryptedtext
    decryptedText = decryptedText & a(x)
Next x
 
'assign first 4 letters & last 4 letters
tmp1 = a(1)
tmp2 = a(2)
tmp3 = a(3)
tmp4 = a(4)
tmp5 = a(textLength - 1)
tmp6 = a(textLength - 2)
tmp7 = a(textLength - 3)
tmp8 = a(textLength)
 
'scramble (switch) letters
a(1) = tmp3
a(2) = tmp6
a(3) = tmp1
a(4) = tmp8
a(textLength - 1) = tmp7
a(textLength - 2) = tmp2
a(textLength - 3) = tmp5
a(textLength) = tmp4
 
 
'put unscrambled letters back into text
For y = 1 To textLength
    unscrambledText = unscrambledText & a(y)
Next y
 
'make sure function returns final decrypted & unscrambled text
subDecrypt = unscrambledText
 
End Function

To encrypt/decrypt the text, call the function and give it the text. For example:

vb Code:

Call subEncrypt("I WANT TO ENCRYPT THIS")