Text nasıl şifrelenir

'encryption function :

Public Function Encrypt(ByVal Plain As String)
For I=1 To Len(Plain) 
Letter=Mid(Plain,I,1)
Mid(Plain,I,1)=Chr(Asc(Letter)+1)
Next
Encrypt = Plain
End Sub

Public Function Decrypt(ByVal Encrypted As String)
For I=1 to Len(Encrypted) 
Letter=Mid(Encrypted,I,1)
Mid(Encrypted,I,1)=Chr(Asc(Letter)-1)
Next
Decrypt = Encrypted
End Sub

Print Encrypt("This is just an example")
Print Decrypt("Uijt!jt!kvtu!bo!fybnqmf")