.NET AES/Rijndael算法 - 重用解密

Question

不一致解密時，我創建了一個類用於加密和使用AES解密。

public class AesEncryptionProvider { 
    #region Fields 

    // Encryption key 
    private static readonly byte[] s_key = new byte[32] { 
     // Omitted... 
    }; 

    // Initialization vector 
    private static readonly byte[] s_iv = new byte[16] { 
     // Omitted... 
    }; 

    private AesCryptoServiceProvider m_provider; 
    private ICryptoTransform m_encryptor; 
    private ICryptoTransform m_decryptor; 

    #endregion 

    #region Constructors 

    private AesEncryptionProvider() { 
     m_provider = new AesCryptoServiceProvider(); 
     m_encryptor = m_provider.CreateEncryptor(s_key, s_iv); 
     m_decryptor = m_provider.CreateDecryptor(s_key, s_iv); 
    } 

    static AesEncryptionProvider() { 
     Instance = new AesEncryptionProvider(); 
    } 

    #endregion 

    #region Properties 

    public static AesEncryptionProvider Instance { get; private set; } 

    #endregion 

    #region Methods 

    public string Encrypt (string value) { 
     if (string.IsNullOrEmpty(value)) { 
      throw new ArgumentException("Value required."); 
     } 

     return Convert.ToBase64String(
      Transform(
       Encoding.UTF8.GetBytes(value), 
       m_encryptor)); 
    } 

    public string Decrypt (string value) { 
     if (string.IsNullOrEmpty(value)) { 
      throw new ArgumentException("Value required."); 
     } 

     return Encoding.UTF8.GetString(
      Transform(
       Convert.FromBase64String(value), 
       m_decryptor)); 
    } 

    #endregion 

    #region Private methods 

    private byte[] Transform (byte[] input, ICryptoTransform transform) { 
     byte[] output; 
     using (MemoryStream memory = new MemoryStream()) { 
      using (CryptoStream crypto = new CryptoStream(
       memory, 
       transform, 
       CryptoStreamMode.Write 
      )) { 
       crypto.Write(input, 0, input.Length); 
       crypto.FlushFinalBlock(); 

       output = memory.ToArray(); 
      } 
     } 
     return output; 
    } 

    #endregion 
} 

正如你可以看到，在這兩種情況下，我通過CryptoStream寫爲MemoryStream。如果我在Decrypt的每個調用中都通過m_provider.CreateDecyptor(s_key, s_iv)創建一個新的解密器，它就可以工作。

出了什麼錯在這裏？爲什麼解密者表現得好像忘記了IV？有沒有什麼呼籲StreamReader.ReadToEnd()這樣做有助於m_decryptor正常工作？

我想避免我在這裏列出的兩種「工作」方法中的任何一種，因爲這兩種方法都會對性能造成影響，這是一條非常關鍵的途徑。提前致謝。

Answer 1

好吧，我承認我不知道爲什麼這個工作，但改變AesCryptoServiceProvider到AesManaged，瞧。

我還建議讓你的類實現IDisposable，因爲它包含了實現它的三個成員變量。請參閱下面的代碼更改：

public sealed class AesEncryptionProvider : IDisposable 
{ 
    // Encryption key 
    private static readonly byte[] key = new byte[] 
    { 
     // Omitted... 
    }; 

    // Initialization vector 
    private static readonly byte[] iv = new byte[] 
    { 
     // Omitted... 
    }; 

    private static readonly AesEncryptionProvider instance = new AesEncryptionProvider(); 

    private readonly AesManaged provider; 

    private readonly ICryptoTransform encryptor; 

    private readonly ICryptoTransform decryptor; 

    private AesEncryptionProvider() 
    { 
     this.provider = new AesManaged(); 
     this.encryptor = this.provider.CreateEncryptor(key, iv); 
     this.decryptor = this.provider.CreateDecryptor(key, iv); 
    } 

    public static AesEncryptionProvider Instance 
    { 
     get 
     { 
      return instance; 
     } 
    } 

    public void Dispose() 
    { 
     this.decryptor.Dispose(); 
     this.encryptor.Dispose(); 
     this.provider.Dispose(); 
     GC.SuppressFinalize(this); 
    } 

    public string Encrypt(string value) 
    { 
     if (string.IsNullOrEmpty(value)) 
     { 
      throw new ArgumentException("Value required."); 
     } 

     return Convert.ToBase64String(Transform(Encoding.UTF8.GetBytes(value), this.encryptor)); 
    } 

    public string Decrypt(string value) 
    { 
     if (string.IsNullOrEmpty(value)) 
     { 
      throw new ArgumentException("Value required."); 
     } 

     return Encoding.UTF8.GetString(Transform(Convert.FromBase64String(value), this.decryptor)); 
    } 

    private static byte[] Transform(byte[] input, ICryptoTransform transform) 
    { 
     using (var memory = new MemoryStream()) 
     using (var crypto = new CryptoStream(memory, transform, CryptoStreamMode.Write)) 
     { 
      crypto.Write(input, 0, input.Length); 
      crypto.FlushFinalBlock(); 
      return memory.ToArray(); 
     } 
    } 
}