Trong bài viết này, chúng ta sẽ sử dụng VBA để mã hoá chuỗi trong VBA. Việc mã hoá chuỗi sẽ giúp chúng ta so sánh 2 chuỗi một cách hiệu quả và nhanh chóng. Các thuật toán được hỗ trợ: MD5, SHA1, SHA2-256, SHA2-384, và SHA2-512

Lưu ý, để chạy được code này, trên máy tính của bạn cần được cài đặt .NET Framework 3.5

Option Explicit

Sub Test()
    'run this to test md5, sha1, sha2/256, sha384, sha2/512 with salt, or sha2/512
    'Check that Net Framework 3.5 (includes .Net 2 and .Net 3 is installed in windows
    'and not just Net Advanced Services 
    
    Dim sIn As String, sOut As String, b64 As Boolean
    Dim sH As String, sSecret As String
    
    'insert the text to hash within the sIn quotes
    'and for selected procedures a string for the secret key
    sIn = ""
    sSecret = "" 'secret key for StrToSHA512Salt only
    
    'select as required
    'b64 = False   'output hex
    b64 = True   'output base-64
    
    'enable any one
    'sH = MD5(sIn, b64)
    'sH = SHA1(sIn, b64)
    'sH = SHA256(sIn, b64)
    'sH = SHA384(sIn, b64)
    'sH = StrToSHA512Salt(sIn, sSecret, b64)
    sH = SHA512(sIn, b64)
    
    'message box and immediate window outputs
    Debug.Print sH & vbNewLine & Len(sH) & " characters in length"
    MsgBox sH & vbNewLine & Len(sH) & " characters in length"
    
    'de-comment this block to place the hash in first cell of sheet1
'    With ThisWorkbook.Worksheets("Sheet1").Cells(1, 1)
'        .Font.Name = "Consolas"
'        .Select: Selection.NumberFormat = "@" 'make cell text
'        .Value = sH
'    End With

End Sub

Public Function MD5(ByVal sIn As String, Optional bB64 As Boolean = 0) As String
    'Set a reference to mscorlib 4.0 64-bit
    'Check that Net Framework 3.5 (includes .Net 2 and .Net 3 is installed in windows
    'and not just Net Advanced Services 
        
    'Test with empty string input:
    'Hex:   d41d8cd98f00...etc
    'Base-64: 1B2M2Y8Asg...etc
        
    Dim oT As Object, oMD5 As Object
    Dim TextToHash() As Byte
    Dim bytes() As Byte
        
    Set oT = CreateObject("System.Text.UTF8Encoding")
    Set oMD5 = CreateObject("System.Security.Cryptography.MD5CryptoServiceProvider")
 
    TextToHash = oT.GetBytes_4(sIn)
    bytes = oMD5.ComputeHash_2((TextToHash))
 
    If bB64 = True Then
       MD5 = ConvToBase64String(bytes)
    Else
       MD5 = ConvToHexString(bytes)
    End If
        
    Set oT = Nothing
    Set oMD5 = Nothing

End Function

Public Function SHA1(sIn As String, Optional bB64 As Boolean = 0) As String
    'Set a reference to mscorlib 4.0 64-bit
    'Check that Net Framework 3.5 (includes .Net 2 and .Net 3 is installed in windows
    'and not just Net Advanced Services 
   
   'Test with empty string input:
    '40 Hex:   da39a3ee5e6...etc
    '28 Base-64:   2jmj7l5rSw0yVb...etc
    
    Dim oT As Object, oSHA1 As Object
    Dim TextToHash() As Byte
    Dim bytes() As Byte
            
    Set oT = CreateObject("System.Text.UTF8Encoding")
    Set oSHA1 = CreateObject("System.Security.Cryptography.SHA1Managed")
    
    TextToHash = oT.GetBytes_4(sIn)
    bytes = oSHA1.ComputeHash_2((TextToHash))
        
    If bB64 = True Then
       SHA1 = ConvToBase64String(bytes)
    Else
       SHA1 = ConvToHexString(bytes)
    End If
            
    Set oT = Nothing
    Set oSHA1 = Nothing
    
End Function

Public Function SHA256(sIn As String, Optional bB64 As Boolean = 0) As String
    'Set a reference to mscorlib 4.0 64-bit
    'Check that Net Framework 3.5 (includes .Net 2 and .Net 3 is installed in windows
    'and not just Net Advanced Services 
    
    'Test with empty string input:
    '64 Hex:   e3b0c44298f...etc
    '44 Base-64:   47DEQpj8HBSa+/...etc
    
    Dim oT As Object, oSHA256 As Object
    Dim TextToHash() As Byte, bytes() As Byte
    
    Set oT = CreateObject("System.Text.UTF8Encoding")
    Set oSHA256 = CreateObject("System.Security.Cryptography.SHA256Managed")
    
    TextToHash = oT.GetBytes_4(sIn)
    bytes = oSHA256.ComputeHash_2((TextToHash))
    
    If bB64 = True Then
       SHA256 = ConvToBase64String(bytes)
    Else
       SHA256 = ConvToHexString(bytes)
    End If
    
    Set oT = Nothing
    Set oSHA256 = Nothing
    
End Function

Public Function SHA384(sIn As String, Optional bB64 As Boolean = 0) As String
    'Set a reference to mscorlib 4.0 64-bit
    'Check that Net Framework 3.5 (includes .Net 2 and .Net 3 is installed in windows
    'and not just Net Advanced Services 
    
    'Test with empty string input:
    '96 Hex:   38b060a751ac...etc
    '64 Base-64:   OLBgp1GsljhM2T...etc
    
    Dim oT As Object, oSHA384 As Object
    Dim TextToHash() As Byte, bytes() As Byte
    
    Set oT = CreateObject("System.Text.UTF8Encoding")
    Set oSHA384 = CreateObject("System.Security.Cryptography.SHA384Managed")
    
    TextToHash = oT.GetBytes_4(sIn)
    bytes = oSHA384.ComputeHash_2((TextToHash))
    
    If bB64 = True Then
       SHA384 = ConvToBase64String(bytes)
    Else
       SHA384 = ConvToHexString(bytes)
    End If
    
    Set oT = Nothing
    Set oSHA384 = Nothing
    
End Function

Public Function SHA512(sIn As String, Optional bB64 As Boolean = 0) As String
    'Set a reference to mscorlib 4.0 64-bit
    'Check that Net Framework 3.5 (includes .Net 2 and .Net 3 is installed in windows
    'and not just Net Advanced Services 
    
    'Test with empty string input:
    '128 Hex:   cf83e1357eefb8bd...etc
    '88 Base-64:   z4PhNX7vuL3xVChQ...etc
    
    Dim oT As Object, oSHA512 As Object
    Dim TextToHash() As Byte, bytes() As Byte
    
    Set oT = CreateObject("System.Text.UTF8Encoding")
    Set oSHA512 = CreateObject("System.Security.Cryptography.SHA512Managed")
    
    TextToHash = oT.GetBytes_4(sIn)
    bytes = oSHA512.ComputeHash_2((TextToHash))
    
    If bB64 = True Then
       SHA512 = ConvToBase64String(bytes)
    Else
       SHA512 = ConvToHexString(bytes)
    End If
    
    Set oT = Nothing
    Set oSHA512 = Nothing
    
End Function

Function StrToSHA512Salt(ByVal sIn As String, ByVal sSecretKey As String, _
                           Optional ByVal b64 As Boolean = False) As String
    'Returns a sha512 STRING HASH in function name, modified by the parameter sSecretKey.
    'This hash differs from that of SHA512 using the SHA512Managed class.
    'HMAC class inputs are hashed twice;first input and key are mixed before hashing,
    'then the key is mixed with the result and hashed again.
    'Check that Net Framework 3.5 (includes .Net 2 and .Net 3 is installed in windows
    'and not just Net Advanced Services 
    
    Dim asc As Object, enc As Object
    Dim TextToHash() As Byte
    Dim SecretKey() As Byte
    Dim bytes() As Byte
    
    'Test results with both strings empty:
    '128 Hex:    b936cee86c9f...etc
    '88 Base-64:   uTbO6Gyfh6pd...etc
    
    'create text and crypto objects
    Set asc = CreateObject("System.Text.UTF8Encoding")
    
    'Any of HMACSHAMD5,HMACSHA1,HMACSHA256,HMACSHA384,or HMACSHA512 can be used
    'for corresponding hashes, albeit not matching those of Managed classes.
    Set enc = CreateObject("System.Security.Cryptography.HMACSHA512")

    'make a byte array of the text to hash
    bytes = asc.Getbytes_4(sIn)
    'make a byte array of the private key
    SecretKey = asc.Getbytes_4(sSecretKey)
    'add the private key property to the encryption object
    enc.Key = SecretKey

    'make a byte array of the hash
    bytes = enc.ComputeHash_2((bytes))
    
    'convert the byte array to string
    If b64 = True Then
       StrToSHA512Salt = ConvToBase64String(bytes)
    Else
       StrToSHA512Salt = ConvToHexString(bytes)
    End If
    
    'release object variables
    Set asc = Nothing
    Set enc = Nothing

End Function

Private Function ConvToBase64String(vIn As Variant) As Variant
    'Check that Net Framework 3.5 (includes .Net 2 and .Net 3 is installed in windows
    'and not just Net Advanced Services 
   
   Dim oD As Object
      
    Set oD = CreateObject("MSXML2.DOMDocument")
      With oD
        .LoadXML "<root />"
        .DocumentElement.DataType = "bin.base64"
        .DocumentElement.nodeTypedValue = vIn
      End With
    ConvToBase64String = Replace(oD.DocumentElement.Text, vbLf, "")
    
    Set oD = Nothing

End Function

Private Function ConvToHexString(vIn As Variant) As Variant
    'Check that Net Framework 3.5 (includes .Net 2 and .Net 3 is installed in windows
    'and not just Net Advanced Services 
    
    Dim oD As Object
      
    Set oD = CreateObject("MSXML2.DOMDocument")
      
      With oD
        .LoadXML "<root />"
        .DocumentElement.DataType = "bin.Hex"
        .DocumentElement.nodeTypedValue = vIn
      End With
    ConvToHexString = Replace(oD.DocumentElement.Text, vbLf, "")
    
    Set oD = Nothing

End Function