Secret Key Encryption Demo

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Secret Key Encryption Demo Preview

Introduction

Using the code

• Pass the selected file to the Encrypt and Decrypt methods below

  Dim path As String = "C:\temp\Encryption\Encrypt-decrypt.doc"
  Dim encrytedPath As String = String.Empty
  
  encrytedPath = Encrypt(path)
  MessageBox.Show("The following file has been encrypted:" & _
                            vbCrLf & vbCrLf & encrytedPath)
  
  path = Decrypt(encrytedPath)
  MessageBox.Show("The following file has been decrypted:" & _
                            vbCrLf & vbCrLf & path)

• Declare the instance of the AES class that will be used to encrypt and decrypt

  'Create the a new instance of AES
  Private mAes As System.Security.Cryptography.Aes = _
                           System.Security.Cryptography.Aes.Create()

• The code for the Encrypt Method
  
  

  ''' <summary>
  ''' This function Encryptes a document and returns the encrypted document path.
  ''' </summary>
  ''' <param name="path">The path of the file to encrypt.</param>
  ''' <returns>The path of the encrypted file.</returns>
  ''' <remarks></remarks>
  Private Function Encrypt(ByVal path As String) As String
  
      Dim outputPath As String = String.Concat(path, ".enc")
  
      'Encryption example using AES
  
      'Get a persisted key and vector
      Dim key As Byte() = GetKey()
      Dim iv As Byte() = GetIV()
  
      'When a new instance of the AES class is created, a new random Key and Vector (IV)
      ' are created automatically. You can use these to encrypt and decrypt your files,
      ' however, they are only good until a new instance of this class is created. Once
      ' a new random Key and Vector (IV) are created, you won't be able to decrypt files, because
      ' the Key and Vector (IV) will have changed. The solution is use them 1 time to 
      ' create a random Key and Vector (IV) (which can be viewed in the Immediate window 
      ' by typing "?mAes.Key" or "?mAes.IV", and pressing Enter), and then somehow persist it 
      ' in your application (like in a class, or in a .DLL, or in an encrypted file or something), 
      ' which I've done as an example in the GeyKey() and GetIV() methods.
  
      'The auto-generated random key can be used by uncommenting these lines, and the corresponding
      ' lines in the Decrypt method below
      'key = mAes.Key
      'iv = mAes.IV
  
      'Create the Encryptor using the Key and Vector (IV)
      Dim encryptor As ICryptoTransform = mAes.CreateEncryptor(GetKey(), GetIV())
  
      'Open both the input file for reading, and
      ' the output file for writing.
      Dim reader As New FileStream(path, FileMode.Open, FileAccess.Read)
      Dim writer As New FileStream(outputPath, FileMode.Create, FileAccess.Write)
  
      'Create an Encrypted Stream using the "encryptor" we created above
      Dim encryptedStream As _
                  New System.Security.Cryptography.CryptoStream(writer, _
                  encryptor, CryptoStreamMode.Write)
  
      Dim bites(1023) As Byte 'Stores 1 KB
      Dim bitesRead As Int32 = 0 'Number of Bytes read
      Dim totalBites As Int64 = 0 'Total Number of Bytes read
  
  
      'Loop through the entire file reading 1 kb at a time
      Do Until totalBites >= reader.Length
  
          bitesRead = reader.Read(bites, 0, 1024) 'Read the bytes from the input file.
  
          encryptedStream.Write(bites, 0, bitesRead) 'Write the encrypted bytes to the output file.
  
          totalBites += bitesRead
  
      Loop
  
  
      'Close and release streams:
      encryptedStream.Close()
      encryptedStream.Dispose()
  
      reader.Close()
      reader.Dispose()
  
      writer.Close()
      writer.Dispose()
  
      'Return the output file
      Return outputPath
  
  End Function

• The code for the Decrypt Method
  
  

  ''' <summary>
  ''' This function Encryptes a document and returns the encrypted document path.
  ''' </summary>
  ''' <param name="path">The path of the file to encrypt.</param>
  ''' <returns>The path of the encrypted file.</returns>
  ''' <remarks></remarks>
  Private Function Decrypt(ByVal path As String) As String
  
      Dim decryptedPath As String = path.Replace(".enc", "")
  
      Dim key As Byte() = GetKey()
      Dim iv As Byte() = GetIV()
  
      'You can use this to generate a new Key and Vector (IV) for use in your applications.
      ' *** Do not use the key that comes with this demo, 
      ' because everyone who uses this demo will have it. ***
      'key = mAes.GenerateKey()
      'iv = mAes.GenerateIV()
  
      'Create the Decryptor using the Key and Vector (IV)
      Dim decryptor As ICryptoTransform = mAes.CreateDecryptor(key, iv)
  
      'Open both the input file for reading, and
      ' the output file for writing.
      Dim reader As New FileStream(path, FileMode.Open, FileAccess.Read)
      Dim writer As New FileStream(decryptedPath, FileMode.Create, FileAccess.Write)
  
      'Create an Encrypted Stream using the "encryptor" we created above
      Dim decryptedStream As _
                      New System.Security.Cryptography.CryptoStream(writer, _
                      decryptor, CryptoStreamMode.Write)
  
      Dim bites(1023) As Byte 'Stores 1 KB
      Dim bitesRead As Int32 = 0 'Number of Bytes read
      Dim totalBites As Int64 = 0 'Total Number of Bytes read
  
  
      'Loop through the entire file reading 1 kb at a time
      Do Until totalBites >= reader.Length
  
         bitesRead = reader.Read(bites, 0, 1024) 'Read the bytes from the input file.
  
         decryptedStream.Write(bites, 0, bitesRead) 'Write the encrypted bytes to the output file.
  
         totalBites += bitesRead
  
      Loop
  
  
      'Close and release streams:
      decryptedStream.Close()
      decryptedStream.Dispose()
  
      reader.Close()
      reader.Dispose()
  
      writer.Close()
      writer.Dispose()
  
      Return decryptedPath
  
  End Function

• Persisted Key and Vector (IV)
  
  

  '*** Just a note - DO NOT USE THIS KEY FOR YOUR OWN ENCRYPTION
  ' Create a new key by using the GenerateKey() method
  Private Function GetKey() As Byte()
  
      '32 length byte array
      Dim key(31) As Byte
      key(0) = 195
      key(1) = 201
      key(2) = 141
      key(3) = 238
      key(4) = 118
      key(5) = 179
      key(6) = 108
      key(7) = 7
      key(8) = 37
      key(9) = 109
      key(10) = 7
      key(11) = 48
      key(12) = 66
      key(13) = 141
      key(14) = 2
      key(15) = 65
      key(16) = 213
      key(17) = 136
      key(18) = 141
      key(19) = 210
      key(20) = 78
      key(21) = 234
      key(22) = 83
      key(23) = 34
      key(24) = 41
      key(25) = 238
      key(26) = 152
      key(27) = 88
      key(28) = 228
      key(29) = 72
      key(30) = 160
      key(31) = 174
  
      Return key
  
  End Function
  
  
  
  '*** Just a note - DO NOT USE THIS Vector (IV) FOR YOUR OWN ENCRYPTION
  ' Create a new Vector (IV) by using the GenerateIV() method
  Private Function GetIV() As Byte()
  
      '16 length byte array
      Dim IV(15) As Byte
      IV(0) = 30
      IV(1) = 185
      IV(2) = 3
      IV(3) = 73
      IV(4) = 26
      IV(5) = 247
      IV(6) = 159
      IV(7) = 124
      IV(8) = 211
      IV(9) = 112
      IV(10) = 251
      IV(11) = 231
      IV(12) = 69
      IV(13) = 25
      IV(14) = 132
      IV(15) = 1
  
      Return IV
  
  End Function

Points of Interest