Simple key 'encryption'

[vbNeo]

Private Function InvertString(sT As String) As String
Dim sTT As String
 
For I = Len(sT) To 1 Step -1
sTT = sTT & Mid(sT, I, 1)
Next
 
InvertString = sTT
 
End Function
 
Private Function Encrypt(sT As String, sKey As String) As String
Dim sEncrypted As String
Dim keyCount As Integer
 
sT = InvertString(sT)
sKey = InvertString(sKey)
keyCount = 1
For I = 1 To Len(sT)
sEncrypted = sEncrypted & Chr(Asc(Mid(sT, I, 1)) + Mid(sKey, keyCount, 1))
keyCount = keyCount + 1
If keyCount > Len(sKey) Then keyCount = 1
Next
 
Encrypt = sEncrypted
 
End Function
 
Private Function Decrypt(sT As String, sKey As String) As String
Dim sDecrypted As String
Dim keyCount As Integer
 
sKey = InvertString(sKey)
keyCount = 1
 
For I = 1 To Len(sT)
sDecrypted = sDecrypted & Chr(Asc(Mid(sT, I, 1)) - Mid(sKey, keyCount, 1))
keyCount = keyCount + 1
If keyCount > Len(sKey) Then keyCount = 1
Next
 
Decrypt = InvertString(sDecrypted)
 
End Function

Just use, Encrypt() And Decrypt() - remember to pass the same key!!

[CVMichael]

Did you try your own code before posting it ?

First of all, it seems that you like to declare variables global (I think)., because variable "I" is not declared anywhere in any of the functions...

Second, I gt a "Type mismatch", at this line:

sEncrypted = sEncrypted & Chr(Asc(Mid(sT, I, 1)) + Mid(sKey, keyCount, 1))

Asc(Mid(sT, I, 1)) returns a number, and you want to add it to character Mid(sKey, keyCount, 1)...

Third, even if I put Chr(Mid(sKey, keyCount, 1)), it will add the 2 numbers togeter, and if the result is over 255, it will also give an error...

Fourth... there are LOTS of other posts with lame addition/substraction encryptions, that are really easy to crack, if you reverse the strings before you encrypt it, it won't add much of a "twist" to it...

Take a look at the encryptions I posted in the CodeBank, even this encryption is better than what you posted, and it's less code than that
VB - 31 Bit Encryption function
And after you look at that one, look at this one:
VB - 128, 160 and 256 Bit File Encryption/Decryption with MD5, SHA1 and SHA256

[vbNeo]

Originally posted by CVMichael
Did you try your own code before posting it ?

First of all, it seems that you like to declare variables global (I think)., because variable "I" is not declared anywhere in any of the functions...

Second, I gt a "Type mismatch", at this line:

sEncrypted = sEncrypted & Chr(Asc(Mid(sT, I, 1)) + Mid(sKey, keyCount, 1))

Asc(Mid(sT, I, 1)) returns a number, and you want to add it to character Mid(sKey, keyCount, 1)...

Third, even if I put Chr(Mid(sKey, keyCount, 1)), it will add the 2 numbers togeter, and if the result is over 255, it will also give an error...

Fourth... there are LOTS of other posts with lame addition/substraction encryptions, that are really easy to crack, if you reverse the strings before you encrypt it, it won't add much of a "twist" to it...

Take a look at the encryptions I posted in the CodeBank, even this encryption is better than what you posted, and it's less code than that
VB - 31 Bit Encryption function
And after you look at that one, look at this one:
VB - 128, 160 and 256 Bit File Encryption/Decryption with MD5, SHA1 and SHA256

Whatever you say, I don't have any problems running the code, and I did call it SIMPLE encryption, furthermore, if you don't like it - don't use it, I really don't care.

[SpeedyDog]

yeah... I got that type mismatch too :-P

[Dave Sell]

He did say it was simple. Here, I converted his code into something that compiles. I like it - It gives you a simple layer of security when you just don't want anyone reading your plaintext and you don't care if they try to hack into it.

Option Explicit
'
Private Const KEY As String = "Key1"
'
 
Private Sub Command1_Click()
    Text2 = Encrypt(Text1, KEY)
End Sub
 
Private Sub Command2_Click()
    Text3 = Decrypt(Text2, KEY)
End Sub
 
Private Function InvertString(sT As String) As String
    Dim sTT As String
    Dim i As Integer
    '
    For i = Len(sT) To 1 Step -1
        sTT = sTT & Mid(sT, i, 1)
    Next
    '
    InvertString = sTT
End Function
 
Private Function Encrypt(sT As String, sKey As String) As String
    Dim strEncrypted As String
    Dim keyCount As Long
    Dim i As Long
    Dim lngTemp1 As Long
    Dim lngTemp2 As Long
    '
    sT = InvertString(sT)
    sKey = InvertString(sKey)
    keyCount = 1
    '
    For i = 1 To Len(sT)
        '
        lngTemp1 = Asc(Mid(sT, i, 1))
        lngTemp2 = Asc(Mid(sKey, keyCount, 1))
        strEncrypted = strEncrypted & Chr(lngTemp1 + lngTemp2)
        keyCount = keyCount + 1
        '
        If keyCount > Len(sKey) Then
            keyCount = 1
        End If
    Next
    '
    Encrypt = strEncrypted
End Function
 
Private Function Decrypt(sT As String, sKey As String) As String
    Dim strDecrypted As String
    Dim keyCount As Integer
    Dim i As Long
    Dim lngTemp1 As Long
    Dim lngTemp2 As Long
    '
    sKey = InvertString(sKey)
    keyCount = 1
    '
    For i = 1 To Len(sT)
        '
        lngTemp1 = Asc(Mid(sT, i, 1))
        lngTemp2 = Asc(Mid(sKey, keyCount, 1))
        strDecrypted = strDecrypted & Chr(lngTemp1 - lngTemp2)
        keyCount = keyCount + 1
        '
        If keyCount > Len(sKey) Then
            keyCount = 1
        End If
    Next
    '
    Decrypt = InvertString(strDecrypted)
End Function

[CVMichael]

It encrypts only strings where the ASCII values are less than 128, and the key has to have the ASCII values less than 128 also.

Encrypt something like this, and you'll see what I mean:

Debug.Print Encrypt(String(20, 254), KEY)

[Dave Sell]

The code author never meant for it to encrypt "binary data". Just the printable ASCII characters. Again, it works very well for what it was designed to do.

[Dave Sell]

Originally posted by CVMichael
VB - 31 Bit Encryption function

This is very cool, too. You're right, much less code. I'm not sure how one would rate it better or worse than the original post, except to see which one is more crackable..?

I think it's cool you got it to work as a single function.

[Maven]

You guys may want to check out CAPICOM. It's bascially a com wrapper around the cryptoapi. Would probably be a easy means for security in your applications.

[dglienna]

Windows 2000 Workstation has a problem with Capicom, that I'm trying to figure out.


EDIT:

As it turns out, it only seems to have a problem with

CAPICOM_ENCRYPTION_ALGORITHM_AES

but,

CAPICOM_ENCRYPTION_ALGORITHM_3DES

works fine under both XP and W2K...

[cdubb07]

when i try it, it only runs once then errors out. any thoughts?