SymmetricAlgorithm 類別

定義

public ref class SymmetricAlgorithm abstract : IDisposable

public abstract class SymmetricAlgorithm : IDisposable

[System.Runtime.InteropServices.ComVisible(true)]
public abstract class SymmetricAlgorithm : IDisposable

type SymmetricAlgorithm = class
    interface IDisposable

[<System.Runtime.InteropServices.ComVisible(true)>]
type SymmetricAlgorithm = class
    interface IDisposable

Public MustInherit Class SymmetricAlgorithm
Implements IDisposable

繼承

Object

SymmetricAlgorithm

衍生

System.Security.Cryptography.Aes

System.Security.Cryptography.DES

System.Security.Cryptography.RC2

System.Security.Cryptography.Rijndael

System.Security.Cryptography.TripleDES

屬性

ComVisibleAttribute

實作

IDisposable

範例

下列程式代碼範例會 Aes 使用 類別搭配指定的 Key 屬性和初始化向量 (IV) 來加密 所 inName指定的檔案，並將加密的結果輸出至 所 outName指定的檔案。 方法 desKey 的 和 desIV 參數是8位元組數組。 您必須安裝高加密套件，才能執行此範例。

void EncryptData( String^ inName, String^ outName, array<Byte>^aesKey, array<Byte>^aesIV )
{
   
   //Create the file streams to handle the input and output files.
   FileStream^ fin = gcnew FileStream( inName,FileMode::Open,FileAccess::Read );
   FileStream^ fout = gcnew FileStream( outName,FileMode::OpenOrCreate,FileAccess::Write );
   fout->SetLength( 0 );
   
   //Create variables to help with read and write.
   array<Byte>^bin = gcnew array<Byte>(100);
   long rdlen = 0; //This is the total number of bytes written.

   long totlen = (long)fin->Length; //This is the total length of the input file.

   int len; //This is the number of bytes to be written at a time.

   Aes^ aes = Aes::Create();

   CryptoStream^ encStream = gcnew CryptoStream( fout,aes->CreateEncryptor( aesKey, aesIV ),CryptoStreamMode::Write );
   Console::WriteLine( "Encrypting..." );
   
   //Read from the input file, then encrypt and write to the output file.
   while ( rdlen < totlen )
   {
      len = fin->Read( bin, 0, 100 );
      encStream->Write( bin, 0, len );
      rdlen = rdlen + len;
      Console::WriteLine( "{0} bytes processed", rdlen );
   }

   encStream->Close();
   fout->Close();
   fin->Close();
}

private static void EncryptData(string inName, string outName, byte[] aesKey, byte[] aesIV)
 {
     //Create the file streams to handle the input and output files.
     FileStream fin = new FileStream(inName, FileMode.Open, FileAccess.Read);
     FileStream fout = new FileStream(outName, FileMode.OpenOrCreate, FileAccess.Write);
     fout.SetLength(0);

     //Create variables to help with read and write.
     byte[] bin = new byte[100]; //This is intermediate storage for the encryption.
     long rdlen = 0;              //This is the total number of bytes written.
     long totlen = fin.Length;    //This is the total length of the input file.
     int len;                     //This is the number of bytes to be written at a time.

     Aes aes = Aes.Create();
     CryptoStream encStream = new CryptoStream(fout, aes.CreateEncryptor(aesKey, aesIV), CryptoStreamMode.Write);

     Console.WriteLine("Encrypting...");

     //Read from the input file, then encrypt and write to the output file.
     while(rdlen < totlen)
     {
         len = fin.Read(bin, 0, 100);
         encStream.Write(bin, 0, len);
         rdlen = rdlen + len;
         Console.WriteLine("{0} bytes processed", rdlen);
     }

     encStream.Close();
     fout.Close();
     fin.Close();
 }

Private Shared Sub EncryptData(inName As String, outName As String, _
rijnKey() As Byte, rijnIV() As Byte)

    'Create the file streams to handle the input and output files.
    Dim fin As New FileStream(inName, FileMode.Open, FileAccess.Read)
    Dim fout As New FileStream(outName, FileMode.OpenOrCreate, _
       FileAccess.Write)
    fout.SetLength(0)
    
    'Create variables to help with read and write.
    Dim bin(100) As Byte 'This is intermediate storage for the encryption.
    Dim rdlen As Long = 0 'This is the total number of bytes written.
    Dim totlen As Long = fin.Length 'Total length of the input file.
    Dim len As Integer 'This is the number of bytes to be written at a time.
    'Creates the default implementation, which is RijndaelManaged.
    Dim rijn As SymmetricAlgorithm = SymmetricAlgorithm.Create()
    Dim encStream As New CryptoStream(fout, _
       rijn.CreateEncryptor(rijnKey, rijnIV), CryptoStreamMode.Write)
    
    Console.WriteLine("Encrypting...")
    
    'Read from the input file, then encrypt and write to the output file.
    While rdlen < totlen
        len = fin.Read(bin, 0, 100)
        encStream.Write(bin, 0, len)
        rdlen = Convert.ToInt32(rdlen + len)
        Console.WriteLine("{0} bytes processed", rdlen)
    End While
    
    encStream.Close()
fout.Close()
fin.Close()
End Sub

備註

衍生自 類別的 SymmetricAlgorithm 類別會使用稱為加密區塊鏈結 (CBC) 的鏈結模式，這需要密鑰 (Key) 和初始化向量 IV () ，才能對數據執行密碼編譯轉換。 若要解密使用其中一個 SymmetricAlgorithm 類別加密的數據，您必須將 Key 屬性和 IV 屬性設定為用於加密的相同值。 若要讓對稱演算法很有用，只有傳送者和接收者才知道秘密密鑰。

Aes、 DES、 RC2和 TripleDES 是對稱演算法的實作。

請注意，使用衍生類別時，從安全性觀點來看，只要在使用 物件完成之後強制垃圾收集就不夠。 您必須在對象上明確呼叫 Clear 方法，以在釋放物件之前，將物件內的任何敏感數據清除為零。 請注意，垃圾收集不會將所收集對象的內容零，只是將記憶體標示為可供重新配置。 因此，垃圾收集物件中包含的數據可能仍存在於未配置記憶體中的記憶體堆積中。 在密碼編譯對象的情況下，此數據可能包含機密資訊，例如金鑰數據或純文字區塊。

保存敏感數據之 .NET Framework 中的所有密碼編譯類別都會實作 Clear 方法。 呼叫時， Clear 方法會以零覆寫物件內的所有敏感數據，然後釋放 物件，以便安全地進行垃圾收集。 當物件已零並釋放時，您應該呼叫 Dispose 方法， disposing 並將 參數設為 True ，以處置與 對象相關聯的所有 Managed 和 Unmanaged 資源。

給實施者的注意事項

當您繼承自 類別時 SymmetricAlgorithm ，必須覆寫下列成員： CreateDecryptor(Byte[], Byte[])、 CreateEncryptor(Byte[], Byte[])、 GenerateIV()和 GenerateKey()。

建構函式

欄位

屬性

方法

明確介面實作

適用於

另請參閱

• 密碼編譯服務