by Andy Carrasco (1 Submission)
Category: Miscellaneous
Compatability: Visual Basic 3.0
Difficulty: Unknown Difficulty
Date Added: Wed 3rd February 2021
Rating: 
(103 Votes)
This class contains two functions which can be helpful in creating an online shareware registration system for your software projects. GenerateKeyCode takes a username, or any other string, and generates a unique human-readable registration code (such as 9397-JQM0LD0YJV from the string: Andy Carrasco). GenerateKeyCode will generate a totally unique registration code over and over again, even for the exact same name! VerifyKeyCode is the partner function, and will verify if a keycode matches a given name.
Side Effects
IMPORTANT NOTE!
Although the codes generated from this algorithm will throughly confuse, and secure your code from, the average user, I make absolutely no gaurantee of security. The average hacker is NOT the average user, and anyone with a fairly general understanding of cyphering could quickly crack these algorithms. On the other hand, there are NO registration code utilities which gaurantee security, it would be foolish to believe that any form of encryption is totally secure. You may freely, and are encouraged to, use this algorithm in your own registration utilities, provided that you fully understand that I do not gaurantee the security of these functions, and that I will take no liability for any losses occuring from your use of these functions. They are primarily intended as a learning facility.
Andy Carrasco
API Declarations
VBcodersOption Explicit
' Name: GenerateKeyCode
'
' Description:
' This little routine generates a keycode for shareware registration in the
' format XXXX-YYYYYYYYYY, based on the Name given as an argument. The first
' four digits are a randomly generated seed value, which makes 8999 possible keycodes
' for people with the same name (like John Smith). The last four digits are
' the actual code.
'
' Written by:
' Andy Carrasco (Copyright 1998)
'
Public Function GenerateKeyCode(sName As String) As String
Dim sRandomSeed As String
Dim sKeyCode As String
Dim X As Long
Dim KeyCounter As Long
Dim PrimaryLetter As Long
Dim CodedLetter As Long
Dim sBuffer As String
Randomize
sRandomSeed = CStr(Int((9999 - 1000 + 1) * Rnd + 1000))
sName = UCase$(sName)
KeyCounter = 1
'Clean up sName so there are no illegal characters.
For X = 1 To Len(sName)
If Asc(Mid$(sName, X, 1)) >= 65 And Asc(Mid$(sName, X, 1)) <= 90 Then sBuffer = sBuffer & Mid$(sName, X, 1)
Next X
sName = sBuffer
'if the name is less than 10 characters long, pad it out with ASCII 65
Do While Len(sName) < 10
sName = sName + Chr$(65)
Loop
For X = 1 To Len(sName)
PrimaryLetter = Asc(Mid$(sName, X, 1))
CodedLetter = PrimaryLetter + CInt(Mid$(sRandomSeed, KeyCounter, 1))
If CodedLetter < 90 Then
sKeyCode = sKeyCode + Chr$(CodedLetter)
Else
sKeyCode = sKeyCode + "0"
End If
'Increment the keycounter
KeyCounter = KeyCounter + 1
If KeyCounter > 4 Then KeyCounter = 1
Next X
GenerateKeyCode = sRandomSeed + "-" + Left$(sKeyCode, 10)
End Function
' Name: VerifyKeyCode
'
' Description:
' Verifies if a given keycode is valid for a given name.
'
' Parameters:
' sName - A string containing the user name to validate the key against
' sKeyCode- A string containins the keycode in the form XXXX-YYYYYYYYYY.
'
Public Function VerifyKeyCode(sName As String, sKeyCode As String) As Boolean
Dim sRandomSeed As String
Dim X As Long
Dim KeyCounter As Long
Dim PrimaryLetter As Long
Dim DecodedKey As String
Dim AntiCodedLetter As Long
Dim sBuffer As String
sRandomSeed = Left$(sKeyCode, InStr(sKeyCode, "-") - 1)
sName = UCase$(sName)
sKeyCode = Right$(sKeyCode, 10)
KeyCounter = 1
'Clean up sName so there are no illegal characters.
For X = 1 To Len(sName)
If Asc(Mid$(sName, X, 1)) >= 65 And Asc(Mid$(sName, X, 1)) <= 90 Then sBuffer = sBuffer & Mid$(sName, X, 1)
Next X
sName = sBuffer
'if the name is less than 10 characters long, pad it out with ASCII 65
Do While Len(sName) < 10
sName = sName + Chr$(65)
Loop
'now, decode the keycode
For X = 1 To Len(sKeyCode)
PrimaryLetter = Asc(Mid$(sKeyCode, X, 1))
AntiCodedLetter = PrimaryLetter - CInt(Mid$(sRandomSeed, KeyCounter, 1))
If PrimaryLetter = 48 Then 'zero
DecodedKey = DecodedKey + Mid$(sName, X, 1) 'Take the corresponding letter from the name
Else
DecodedKey = DecodedKey + Chr$(AntiCodedLetter)
End If
'Increment the keycounter
KeyCounter = KeyCounter + 1
If KeyCounter > 4 Then KeyCounter = 1
Next X
If DecodedKey = Left$(sName, 10) Then
VerifyKeyCode = True
Else
VerifyKeyCode = False
End If
End Function