We can see if the file is tempering or not using Cryptography
Code:
Imports System.IO
Imports System.Security.Cryptography
Public Class Form1
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
Application.Exit()
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
OpenFileDialog1.Title = "Open File"
OpenFileDialog1.Filter = "Files (*.*)|*.*"
If OpenFileDialog1.ShowDialog = Windows.Forms.DialogResult.Cancel Then
Exit Sub
End If
Dim sFilePath As String = OpenFileDialog1.FileName
If System.IO.File.Exists(sFilePath) = False Then
sFilePath = ""
Exit Sub
Else
TextBox1.Text = sFilePath
End If
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
OpenFileDialog1.Title = "Open File"
OpenFileDialog1.Filter = "Files (*.*)|*.*"
If OpenFileDialog1.ShowDialog = Windows.Forms.DialogResult.Cancel Then
Exit Sub
End If
Dim sFilePath As String = OpenFileDialog1.FileName
If System.IO.File.Exists(sFilePath) = False Then
sFilePath = ""
Exit Sub
Else
TextBox2.Text = sFilePath
End If
End Sub
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
Dim myHash As HashAlgorithm
myHash = HashAlgorithm.Create()
If TextBox2.Text = String.Empty Or Me.TextBox1.Text = String.Empty Then
MessageBox.Show("Set all form fields prior to initiating a test", _
"Missing Form Data", MessageBoxButtons.OK)
End If
Dim fs1 As New FileStream(TextBox2.Text, FileMode.OpenOrCreate)
Dim fs1Bytes As Byte() = New Byte(fs1.Length) {}
fs1.Read(fs1Bytes, 0, fs1.Length)
Dim arr1() As Byte = myHash.ComputeHash(fs1Bytes)
fs1.Close()
Dim fs2 As New FileStream(TextBox1.Text, FileMode.OpenOrCreate)
Dim fs2Bytes As Byte() = New Byte(fs2.Length) {}
fs2.Read(fs2Bytes, 0, fs2.Length)
Dim arr2() As Byte = myHash.ComputeHash(fs2Bytes)
fs2.Close()
If BitConverter.ToString(arr1) = BitConverter.ToString(arr2) Then
MessageBox.Show("The file examined has not been tampered with.", "Hash" & _
"Test Passed")
'display comparison
MessageBox.Show("Original Hash: " & Environment.NewLine &
BitConverter.ToString(arr1) & _
Environment.NewLine & _
"Test Hash: " & Environment.NewLine & _
BitConverter.ToString(arr2), "Hash Test Results")
Else
MessageBox.Show("The file examined has been tampered with.", "Hash Test Failed")
'display comparison
MessageBox.Show("Original Hash: " & Environment.NewLine &
BitConverter.ToString(arr1) & _
Environment.NewLine & _
"Test Hash: " & Environment.NewLine & _
BitConverter.ToString(arr2), "Hash Test Results")
End If
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
'Dim myhash As Byte
'Dim fs1 As New FileStream(TextBox2.Text, FileMode.OpenOrCreate)
'Dim fs1Bytes As Byte() = New Byte(fs1.Length) {}
'fs1.Read(fs1Bytes, 0, fs1.Length)
'Dim arr1() As Byte = myhash.CompareTo(fs1Bytes)
'fs1.Close()
Dim fs1 As New FileStream(TextBox2.Text, FileMode.OpenOrCreate)
Dim fs1Bytes As Byte() = New Byte(fs1.Length) {}
fs1.Read(fs1Bytes, 0, fs1.Length)
fs1.Close()
Dim fs2 As New FileStream(TextBox1.Text, FileMode.OpenOrCreate)
Dim fs2Bytes As Byte() = New Byte(fs2.Length) {}
fs2.Read(fs2Bytes, 0, fs2.Length)
fs2.Close()
Dim i As Integer = 0
For i = 0 To fs1Bytes.Length - 1
If Not fs1Bytes(i) = fs2Bytes(i) Then
MessageBox.Show("The file examined has been tampered with at position " & _
i.ToString(), "Byte Test Failed")
Exit Sub
End If
Next
MessageBox.Show("The file examined has not been tampered with.", "Byte Test Passed")
End Sub
End Class
