XOR 算法

Attribute VB_Name = "XORCrypto"
'Original Author or Source: VBxtras' VBHowTo Issue #33 - January 10, 2000
' Demonstrates XOR encryption and decryption in a unique way Option Explicit Const
ENCRYPT_OFFSET As Integer = 3
Const ENCRYPT_BASE As Integer = 7
Function EncryptString(ByVal sSource As String) As String
Dim sEncrypted As String
Dim nLength As Long
Dim nLoop As Long
Dim nTemp As Integer
nLength = Len(sSource)
sEncrypted = Space$(nLength)
For nLoop = 1 To nLength
nTemp = Asc(Mid$(sSource, nLoop, 1))
If nLoop Mod 2 Then
nTemp = nTemp - ENCRYPT_OFFSET
Else
nTemp = nTemp + ENCRYPT_OFFSET
End If
nTemp = nTemp Xor (ENCRYPT_BASE - ENCRYPT_OFFSET)
Mid$(sEncrypted, nLoop, 1) = Chr$(nTemp)
Next
EncryptString = sEncrypted

End Function Function DecryptString(ByVal sSource As String) As String
Dim sDecrypted As String
Dim nLength As Long
Dim nLoop As Long
Dim nTemp As Integer
nLength = Len(sSource)
sDecrypted = Space$(nLength)
For nLoop = 1 To nLength
nTemp = Asc(Mid$(sSource, nLoop, 1)) Xor (ENCRYPT_BASE - ENCRYPT_OFFSET)
If nLoop Mod 2 Then
nTemp = nTemp + ENCRYPT_OFFSET
Else
nTemp = nTemp - ENCRYPT_OFFSET
End If
Mid$(sDecrypted, nLoop, 1) = Chr$(nTemp)
Next
DecryptString = sDecrypted
End Function