SymmetricAlgorithm 类

定义

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

继承

Object

SymmetricAlgorithm

派生

System.Security.Cryptography.Aes

System.Security.Cryptography.DES

System.Security.Cryptography.RC2

System.Security.Cryptography.Rijndael

System.Security.Cryptography.TripleDES

属性

ComVisibleAttribute

实现

IDisposable

示例

下面的代码示例使用 Aes 具有指定 Key 属性的 类和初始化向量 (IV) 来加密 由 inName指定的文件，并将加密结果输出到 指定的 outName文件。 desKey方法的 和 desIV 参数是 8 字节数组。 必须安装高加密包才能运行此示例。

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

注解

从 SymmetricAlgorithm 类派生的类使用称为密码块链接 (CBC) 链接模式，这需要密钥 (Key) 和初始化向量 (IV) 对数据执行加密转换。 若要解密使用其中一个SymmetricAlgorithm类加密的数据，必须将 属性和 IV 属性设置为Key用于加密的相同值。 要使对称算法有用，密钥必须只有发送方和接收方知道。

Aes、 DES、 RC2和 TripleDES 是对称算法的实现。

请注意，使用派生类时，从安全角度来看，仅仅在对象使用完后强制垃圾回收是不够的。 您必须对 对象显式调用 Clear 方法，以在释放对象之前将对象中的任何敏感数据归零。 请注意，垃圾回收不会将回收的对象的内容归零，而只是将内存标记为可用于重新分配。 因此，垃圾回收对象中包含的数据可能仍存在于未分配内存的内存堆中。 对于加密对象，此数据可能包含敏感信息，例如密钥数据或纯文本块。

.NET Framework中保存敏感数据的所有加密类都实现 方法Clear。 调用时， Clear 方法用零覆盖 对象中的所有敏感数据，然后释放对象，以便可以安全地对其进行垃圾回收。 当对象被归零并释放后，应调用 Dispose 方法，并将 disposing 参数设置为 True 以释放与对象关联的所有托管和非托管资源。

实施者说明

从 SymmetricAlgorithm 类继承时，必须重写以下成员： CreateDecryptor(Byte[], Byte[])、 CreateEncryptor(Byte[], Byte[])、 GenerateIV()和 GenerateKey()。

构造函数

字段

属性

方法

显式接口实现

适用于

另请参阅

• 加密服务