????????Í???????ɂ́H?mC#?^VB?n?F.NET TIPS

Imports System.Console
Imports System.IO
Imports System.Security.Cryptography
Imports System.Text

' ???͕??????AES?Í???????Base64?`???ŕԂ????\?b?h
Async Function EncryptToBase64(plainText As String, key As Byte(), iv As Byte()) As Task(Of String)
  ' ???͕???????o?C?g?^?z??ɕϊ?
  Dim src() As Byte = Encoding.Unicode.GetBytes(plainText)
  WriteLine($"?????̃o?C?g?^?z??̒???={src.Length}")
  ' ?o?͗?F?????̃o?C?g?^?z??̒???=60

  ' Encryptor?i?Í?????j??p?ӂ???
  Using am = New AesManaged()
    Using encryptor = am.CreateEncryptor(key, iv)
      ' ?t?@?C??????͂Ƃ???Ȃ?A?????Ńt?@?C?????J??
      'Using inStream = New FileStream(FilePath, ?c?c?ȗ??c?c
      ' ?o?̓X?g???[????p?ӂ???
      Using outStream = New MemoryStream()
        ' ?Í??????ď????o??
        Using cs = New CryptoStream(outStream, encryptor, CryptoStreamMode.Write)
          Await cs.WriteAsync(src, 0, src.Length)
          ' ???͂??t?@?C???Ȃ?AinStream??????ʂ??ƒo?C?g?o?b?t?@?[?ɓǂݍ????
          ' cse.Write?ŏ??????ޏ??????J??Ԃ??i?????̃T???v???R?[?h???Q?Ɓj
        End Using
        ' ?o?͂??t?@?C???Ȃ?A?ȏ?Ŋ???

        ' Base64??????ɕϊ????ĕԂ?
        Dim result() As Byte = outStream.ToArray()
        WriteLine($"?Í??̃o?C?g?^?z??̒???={result.Length}")
        ' ?o?͗?F?Í??̃o?C?g?^?z??̒???=64
        ' ?o?̓T?C?Y??BlockSize?i????l16?o?C?g?j?̔{???ɂȂ?
        Return Convert.ToBase64String(result)
      End Using
    End Using
  End Using
End Function

' ?Í??????ꂽBase64?`???̓??͕??????AES???????ĕ????̕??????Ԃ????\?b?h
Async Function DecryptFromBase64(base64Text As String, key As Byte(), iv As Byte()) As Task(Of String)
  ' Base64????????o?C?g?^?z??ɕϊ?
  Dim src() As Byte = Convert.FromBase64String(base64Text)

  ' Decryptor?i??????j??p?ӂ???
  Using am = New AesManaged()
    Using decryptor = am.CreateDecryptor(key, iv)
      ' ???̓X?g???[?????J??
      Using inStream = New MemoryStream(src, False)
        ' ?o?̓X?g???[????p?ӂ???
        Using outStream = New MemoryStream()
          ' ???????Ĉ??ʂ??“ǂݏo???A??????o?̓X?g???[???ɏ????o??
          Using cs = New CryptoStream(inStream, decryptor, CryptoStreamMode.Read)
            Dim buffer(4095) As Byte
            Dim len As Integer = Await cs.ReadAsync(buffer, 0, 4096)
            While (len > 0)
              outStream.Write(buffer, 0, len)
              len = Await cs.ReadAsync(buffer, 0, 4096)
            End While
          End Using
          ' ?o?͂??t?@?C???Ȃ?A?ȏ?Ŋ???

          ' ??????ɕϊ????ĕԂ?
          Dim result() As Byte = outStream.ToArray()
          Return Encoding.Unicode.GetString(result)
        End Using
      End Using
    End Using
  End Using
End Function

' ??L?̈Í????^???????\?b?h???g????
Async Sub CryptoSample()
  ' Key??IV?i???j
  Dim key() As Byte _
    = {
        &HED, &HB, &H56, &HAF, &H61, &HA2, &H71, &H39,
        &HE0, &H4B, &HDC, &HC9, &H23, &H69, &H8C, &HBD,
        &HB9, &H86, &H98, &H28, &HC8, &H3E, &H62, &HA7,
        &HFA, &H17, &HC1, &H33, &H64, &HBF, &H96, &H24
      }
  Dim iv() As Byte _
    = {
        &H6F, &HDF, &H98, &H0, &H67, &H36, &H7D, &H3B,
        &HFF, &HC9, &H3B, &H79, &H4D, &HD4, &H81, &H72
      }

  ' ?Í?????????????
  Dim plainText As String = "?Ɩ??A?v??Insider?͋Ɩ??A?v???J???҂̂??߂̃T?C?g?ł?"

  ' ?Í???
  Dim encrypted As String = Await EncryptToBase64(plainText, key, iv)
  WriteLine($"'{encrypted}'")
  ' ?o?́F'CUiUxGqvU1az7THf81lpEmijZrIn?c?c?ȗ??c?c9Vr38ouENvfcaV0en5uw=='

  ' ????
  Dim decrypted As String = Await DecryptFromBase64(encrypted, key, iv)
  WriteLine($"'{decrypted}'")
  ' ?o?́F'?Ɩ??A?v??Insider?͋Ɩ??A?v???J???҂̂??߂̃T?C?g?ł?'
End Sub

' ?`???̃T???v???R?[?h?Ɏ?????using???K?v

' ?o?C?g?z???\?????郁?\?b?h
Function ByteArrayToHex(array As Byte()) As String
  Return $"{array.Length} bytes, {String.Join(" ", array.Select(Function(b) b.ToString("X2")).ToArray())}"
End Function

?c?c?ȗ??c?c

Using am = New AesManaged()
  ' ????l?̊m?F
  WriteLine($"BlockSize = {am.BlockSize / 8} bytes")
  ' ?o?́FBlockSize = 16 bytes
  WriteLine($"KeySize = {am.KeySize / 8} bytes")
  ' ?o?́FKeySize = 32 bytes
  WriteLine($"Mode = {am.Mode.GetType().Name}.{am.Mode}")
  ' ?o?́FMode = CipherMode.CBC
  WriteLine($"Padding = {am.Padding.GetType().Name}.{am.Padding}")
  ' ?o?́FPadding = PaddingMode.PKCS7

  ' ???????????ꂽKey??IV?iInitialization Vector?j
  WriteLine($"Key: {ByteArrayToHex(am.Key)}")
  ' ?o?͗?FKey: 32 bytes, ED 0B 56 AF 61 A2 71 39 E0 4B DC C9 23 69 8C BD B9 86 98 28 C8 3E 62 A7 FA 17 C1 33 64 BF 96 24
  WriteLine($"IV:  {ByteArrayToHex(am.IV)}")
  ' ?o?͗?FIV:  16 bytes, 6F DF 98 00 67 36 7D 3B FF C9 3B 79 4D D4 81 72
End Using