VBA Reading 2GB+ files in binary in VBA and File Hashes Code for Calculating File Hash in a Standard module

Example

Private Const HashTypeMD5 As String = "MD5" ' https://msdn.microsoft.com/en-us/library/system.security.cryptography.md5cryptoserviceprovider(v=vs.110).aspx
Private Const HashTypeSHA1 As String = "SHA1" ' https://msdn.microsoft.com/en-us/library/system.security.cryptography.sha1cryptoserviceprovider(v=vs.110).aspx
Private Const HashTypeSHA256 As String = "SHA256" ' https://msdn.microsoft.com/en-us/library/system.security.cryptography.sha256cryptoserviceprovider(v=vs.110).aspx
Private Const HashTypeSHA384 As String = "SHA384" ' https://msdn.microsoft.com/en-us/library/system.security.cryptography.sha384cryptoserviceprovider(v=vs.110).aspx
Private Const HashTypeSHA512 As String = "SHA512" ' https://msdn.microsoft.com/en-us/library/system.security.cryptography.sha512cryptoserviceprovider(v=vs.110).aspx

Private uFileSize As Double ' Comment out if not testing performance by FileHashes()

Sub FileHashes()
    Dim tStart As Date, tFinish As Date, sHash As String, aTestFiles As Variant, oTestFile As Variant, aBlockSizes As Variant, oBlockSize As Variant
    Dim BLOCKSIZE As Double
    
    ' This performs performance testing on different file sizes and block sizes
    aBlockSizes = Array("2^12-1", "2^13-1", "2^14-1", "2^15-1", "2^16-1", "2^17-1", "2^18-1", "2^19-1", "2^20-1", "2^21-1", "2^22-1", "2^23-1", "2^24-1", "2^25-1", "2^26-1")
    aTestFiles = Array("C:\ISO\clonezilla-live-2.2.2-37-amd64.iso", "C:\ISO\HPIP201.2014_0902.29.iso", "C:\ISO\SW_DVD5_Windows_Vista_Business_W32_32BIT_English.ISO", "C:\ISO\Win10_1607_English_x64.iso", "C:\ISO\SW_DVD9_Windows_Svr_Std_and_DataCtr_2012_R2_64Bit_English.ISO")
    Debug.Print "Test files: " & Join(aTestFiles, " | ")
    Debug.Print "BlockSizes: " & Join(aBlockSizes, " | ")
    For Each oTestFile In aTestFiles
        Debug.Print oTestFile
        For Each oBlockSize In aBlockSizes
            BLOCKSIZE = Evaluate(oBlockSize)
            tStart = Now
            sHash = GetFileHash(CStr(oTestFile), BLOCKSIZE, HashTypeMD5)
            tFinish = Now
            Debug.Print sHash, uFileSize, Format(tFinish - tStart, "hh:mm:ss"), oBlockSize & " (" & BLOCKSIZE & ")"
        Next
    Next
End Sub

Private Function GetFileHash(ByVal sFile As String, ByVal uBlockSize As Double, ByVal sHashType As String) As String
    Dim oFSO As Object ' "Scripting.FileSystemObject"
    Dim oCSP As Object ' One of the "CryptoServiceProvider"
    Dim oRnd As Random ' "Random" Class by Microsoft, must be in the same file
    Dim uBytesRead As Double, uBytesToRead As Double, bDone As Boolean
    Dim aBlock() As Byte, aBytes As Variant ' Arrays to store bytes
    Dim aHash() As Byte, sHash As String, i As Long
    'Dim uFileSize As Double ' Un-Comment if GetFileHash() is to be used individually
    
    Set oRnd = New Random ' Class by Microsoft: Random
    Set oFSO = CreateObject("Scripting.FileSystemObject")
    Set oCSP = CreateObject("System.Security.Cryptography." & sHashType & "CryptoServiceProvider")
    
    If oFSO Is Nothing Or oRnd Is Nothing Or oCSP Is Nothing Then
        MsgBox "One or more required objects cannot be created"
        GoTo CleanUp
    End If
    
    uFileSize = oFSO.GetFile(sFile).Size ' FILELEN() has 2GB max!
    uBytesRead = 0
    bDone = False
    sHash = String(oCSP.HashSize / 4, "0") ' Each hexadecimal has 4 bits
    
    Application.ScreenUpdating = False
    ' Process the file in chunks of uBlockSize or less
    If uFileSize = 0 Then
        ReDim aBlock(0)
        oCSP.TransformFinalBlock aBlock, 0, 0
        bDone = True
    Else
        With oRnd
            .OpenFile sFile
            Do
                If uBytesRead + uBlockSize < uFileSize Then
                    uBytesToRead = uBlockSize
                Else
                    uBytesToRead = uFileSize - uBytesRead
                    bDone = True
                End If
                ' Read in some bytes
                aBytes = .ReadBytes(uBytesToRead)
                aBlock = aBytes
                If bDone Then
                    oCSP.TransformFinalBlock aBlock, 0, uBytesToRead
                    uBytesRead = uBytesRead + uBytesToRead
                Else
                    uBytesRead = uBytesRead + oCSP.TransformBlock(aBlock, 0, uBytesToRead, aBlock, 0)
                End If
                DoEvents
            Loop Until bDone
            .CloseFile
        End With
    End If
    If bDone Then
        ' convert Hash byte array to an hexadecimal string
        aHash = oCSP.hash
        For i = 0 To UBound(aHash)
            Mid$(sHash, i * 2 + (aHash(i) > 15) + 2) = Hex(aHash(i))
        Next
    End If
    Application.ScreenUpdating = True
    ' Clean up
    oCSP.Clear
CleanUp:
    Set oFSO = Nothing
    Set oRnd = Nothing
    Set oCSP = Nothing
    GetFileHash = sHash
End Function

The output is pretty interesting, my test files indicates that BLOCKSIZE = 131071 (2^17-1) gives overall best performance with 32bit Office 2010 on Windows 7 x64, next best is 2^16-1 (65535). Note 2^27-1 yields Out of memory.

File Size (bytes)	File Name
146,800,640	clonezilla-live-2.2.2-37-amd64.iso
798,210,048	HPIP201.2014_0902.29.iso
2,073,016,320	SW_DVD5_Windows_Vista_Business_W32_32BIT_English.ISO
4,380,387,328	Win10_1607_English_x64.iso
5,400,115,200	SW_DVD9_Windows_Svr_Std_and_DataCtr_2012_R2_64Bit_English.ISO