在 VB.NET 中，将 AES 密钥和加密数据写入相同的 MemoryStream 不起作用

Question

我正在尝试使用对称加密来加密一些数据，并将解密所需的密钥与数据一起存储在 MemoryStream 中。 （虽然我知道仅此一项在安全方面确实很愚蠢，但我将使用 RSA 来加密对称密钥。不过，现在，我正试图让这部分工作。）

我正在使用 FileHelpers 库为我的分隔符解析数据（分号，因为我不相信数据中会有分号）。不幸的是，在我的解密函数中，当它解析时，它只返回一条记录。而且，如果我显示在此函数末尾创建的整个加密数据字符串，它似乎并没有使用多条记录。

我想知道当我创建新的加密流时，它是否默认为内存流的开头，所以当我写入加密数据时，它会覆盖我刚刚写入内存流的数据。你觉得对吗？

感谢您的帮助！

Private Function Encrypt(ByVal data As String) As String
    Dim utf8 As New UTF8Encoding
    ' Convert string data to byte array
    Dim inBytes() As Byte = utf8.GetBytes(data)
    ' Create memory stream for storing the data we've manipulated
    Dim ms As New MemoryStream()

    Dim aes As New RijndaelManaged()
    aes.KeySize = 256

    Dim cs As New CryptoStream(ms, aes.CreateEncryptor(), CryptoStreamMode.Write)

    ' Write key to beginning of memory stream
    ms.Write(aes.Key, 0, aes.Key.Length)
    ' Add semicolon delimiter to memory stream
    ms.Write(utf8.GetBytes(";"), 0, utf8.GetBytes(";").Length)
    ' Write IV to memory stream
    ms.Write(aes.IV, 0, aes.IV.Length)
    ' Write semicolon delimiter to memory stream
    ms.Write(utf8.GetBytes(";"), 0, utf8.GetBytes(";").Length)
    ' Ensure that the data we've just written is in the memory stream, before
    ' we add the encrypted data
    ms.Flush()

    ' Write the encrypted data
    cs.Write(inBytes, 0, inBytes.Length) ' encrypt
    cs.FlushFinalBlock()

    ' Return encrypted data as string
    Return Convert.ToBase64String(ms.GetBuffer(), 0, ms.Length)
End Function

Answer 1

以下是如何实现此目标的快速示例。我将Encrypt 和Decrypt 都包括在内，因为在两边都遵循相同的模式显然很重要。我会把相关的错误检查等留给你:)

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

Module Module1

  Sub Main()
    Dim encrypted As String = Encrypt("Here is the data")
    Dim decrypted As String = Decrypt(encrypted)
    Console.WriteLine(decrypted)
    Console.ReadKey()
  End Sub

  Private Function Encrypt(clearText As String) As String
    Dim aes As New RijndaelManaged
    aes.KeySize = 256

    Using ms As New MemoryStream
      ms.WriteByte(aes.Key.Length)
      ms.Write(aes.Key, 0, aes.Key.Length)
      ms.WriteByte(aes.IV.Length)
      ms.Write(aes.IV, 0, aes.IV.Length)

      Using cs As New CryptoStream(ms, aes.CreateEncryptor(), CryptoStreamMode.Write)
        Dim bytes() As Byte = Encoding.UTF8.GetBytes(clearText)
        cs.Write(bytes, 0, bytes.Length)
      End Using

      Return Convert.ToBase64String(ms.ToArray())
    End Using
  End Function

  Private Function Decrypt(cipherText As String) As String
    Dim ms As New MemoryStream(Convert.FromBase64String(cipherText))

    Dim keyLength As Byte = ms.ReadByte()
    Dim key(keyLength - 1) As Byte
    ms.Read(key, 0, keyLength)

    Dim ivLength As Byte = ms.ReadByte()
    Dim iv(ivLength - 1) As Byte
    ms.Read(iv, 0, ivLength)

    Dim dataOffset As Integer = ms.Position

    Dim aes As New RijndaelManaged()
    aes.Key = key
    aes.IV = iv

    Using cs As New CryptoStream(ms, aes.CreateDecryptor(), CryptoStreamMode.Read)
      Using sr As New StreamReader(cs, Encoding.UTF8)
        Return sr.ReadToEnd()
      End Using
    End Using
  End Function
End Module

Answer 2

你为什么要写内存流？直接写入 Crypto 流，然后从内存流中读取加密数据。这是 AES 加密的 C# 版本。

aesEncryptor 是你的aes.CreateEncryptor()

        private byte[] encryptWithAes(ICryptoTransform aesEncryptor, byte[] data)
        {
            MemoryStream memStream = null; //stream to write encrypted data to
            CryptoStream cryptoStream = null; //crypto stream to encrypt data

            try
            {
                memStream = new MemoryStream(); 

                //initiate crypto stream telling it to write the encrypted data to the memory stream
                cryptoStream = new CryptoStream(memStream, aesEncryptor, CryptoStreamMode.Write);

                //write the data to the memory stream
                cryptoStream.Write(data, 0, data.Length);
            }
            catch (Exception ee)
            {
                //rethrow
                throw new Exception("Error while encrypting with AES: ", ee);
            }
            finally
            {
                //close 'em
                if (cryptoStream != null)
                    cryptoStream.Close();
                if (memStream != null)
                    memStream.Close();
            }

            //return the encrypted data
            return memStream.ToArray();
        }

可以这样调用：

public byte[] doEncrypt(byte[] dataToEncrypt)
{
            RijndaelManaged aesAlg = new RijndaelManaged();
            aesAlg.KeySize = AES_KEY_SIZE;
            aesAlg.GenerateKey();
            aesAlg.GenerateIV();
            aesAlg.Mode = CipherMode.CBC;
            aesAlg.Padding = PaddingMode.PKCS7;

            byte[] aesKey = aesAlg.Key;
            byte[] aesIV = aesAlg.IV;

            byte[] encryptedData = encryptWithAes(aesAlg.CreateEncryptor(), dataToEncrypt);

            //store your aesKey, aesIV, and encryptedData together however you want
}

您不应该使用任何字符删除二进制数据，因为当您再次读取该数据时，您必须对整个缓冲区进行编码，包括密钥和 IV，一旦编码，您的分隔符可能会随机出现在任何地方。而是将密钥的长度存储为一个字节，然后再存储密钥。当你去读回数据时，你可以把第一个字节（密钥长度）读成一个整数，然后知道要读多少才能得到密钥。这对你有意义吗？