HMACSHA256 类

定义

使用 SHA256 哈希函数计算基于哈希值的消息验证代码 (HMAC)。

public ref class HMACSHA256 : System::Security::Cryptography::HMAC
[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public class HMACSHA256 : System.Security.Cryptography.HMAC
public class HMACSHA256 : System.Security.Cryptography.HMAC
[System.Runtime.InteropServices.ComVisible(true)]
public class HMACSHA256 : System.Security.Cryptography.HMAC
[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
type HMACSHA256 = class
    inherit HMAC
type HMACSHA256 = class
    inherit HMAC
[<System.Runtime.InteropServices.ComVisible(true)>]
type HMACSHA256 = class
    inherit HMAC
Public Class HMACSHA256
Inherits HMAC
继承
属性

示例

以下示例演示如何使用 HMACSHA256 对象对文件进行签名,然后如何验证该文件。

using namespace System;
using namespace System::IO;
using namespace System::Security::Cryptography;

// Computes a keyed hash for a source file, creates a target file with the keyed hash
// prepended to the contents of the source file, then decodes the file and compares
// the source and the decoded files.
void EncodeFile( array<Byte>^key, String^ sourceFile, String^ destFile )
{
   
   // Initialize the keyed hash object.
   HMACSHA256^ myhmacsha256 = gcnew HMACSHA256( key );
   FileStream^ inStream = gcnew FileStream( sourceFile,FileMode::Open );
   FileStream^ outStream = gcnew FileStream( destFile,FileMode::Create );
   
   // Compute the hash of the input file.
   array<Byte>^hashValue = myhmacsha256->ComputeHash( inStream );
   
   // Reset inStream to the beginning of the file.
   inStream->Position = 0;
   
   // Write the computed hash value to the output file.
   outStream->Write( hashValue, 0, hashValue->Length );
   
   // Copy the contents of the sourceFile to the destFile.
   int bytesRead;
   
   // read 1K at a time
   array<Byte>^buffer = gcnew array<Byte>(1024);
   do
   {
      
      // Read from the wrapping CryptoStream.
      bytesRead = inStream->Read( buffer, 0, 1024 );
      outStream->Write( buffer, 0, bytesRead );
   }
   while ( bytesRead > 0 );

   myhmacsha256->Clear();
   
   // Close the streams
   inStream->Close();
   outStream->Close();
   return;
} // end EncodeFile



// Decode the encoded file and compare to original file.
bool DecodeFile( array<Byte>^key, String^ sourceFile )
{
   
   // Initialize the keyed hash object. 
   HMACSHA256^ hmacsha256 = gcnew HMACSHA256( key );
   
   // Create an array to hold the keyed hash value read from the file.
   array<Byte>^storedHash = gcnew array<Byte>(hmacsha256->HashSize / 8);
   
   // Create a FileStream for the source file.
   FileStream^ inStream = gcnew FileStream( sourceFile,FileMode::Open );
   
   // Read in the storedHash.
   inStream->Read( storedHash, 0, storedHash->Length );
   
   // Compute the hash of the remaining contents of the file.
   // The stream is properly positioned at the beginning of the content, 
   // immediately after the stored hash value.
   array<Byte>^computedHash = hmacsha256->ComputeHash( inStream );
   
   // compare the computed hash with the stored value
   bool err = false;
   for ( int i = 0; i < storedHash->Length; i++ )
   {
      if ( computedHash[ i ] != storedHash[ i ] )
      {
         err = true;
      }
   }
   if (err)
        {
            Console::WriteLine("Hash values differ! Encoded file has been tampered with!");
            return false;
        }
        else
        {
            Console::WriteLine("Hash values agree -- no tampering occurred.");
            return true;
        }

} //end DecodeFile


int main()
{
   array<String^>^Fileargs = Environment::GetCommandLineArgs();
   String^ usageText = "Usage: HMACSHA256 inputfile.txt encodedfile.hsh\nYou must specify the two file names. Only the first file must exist.\n";
   
   //If no file names are specified, write usage text.
   if ( Fileargs->Length < 3 )
   {
      Console::WriteLine( usageText );
   }
   else
   {
      try
      {
         
         // Create a random key using a random number generator. This would be the
         //  secret key shared by sender and receiver.
         array<Byte>^secretkey = gcnew array<Byte>(64);
         
         //RNGCryptoServiceProvider is an implementation of a random number generator.
         RNGCryptoServiceProvider^ rng = gcnew RNGCryptoServiceProvider;
         
         // The array is now filled with cryptographically strong random bytes.
         rng->GetBytes( secretkey );
         
         // Use the secret key to encode the message file.
         EncodeFile( secretkey, Fileargs[ 1 ], Fileargs[ 2 ] );
         
         // Take the encoded file and decode
         DecodeFile( secretkey, Fileargs[ 2 ] );
      }
      catch ( IOException^ e ) 
      {
         Console::WriteLine( "Error: File not found", e );
      }

   }
} //end main
using System;
using System.IO;
using System.Security.Cryptography;

public class HMACSHA256example
{

    public static void Main(string[] Fileargs)
    {
        string dataFile;
        string signedFile;
        //If no file names are specified, create them.
        if (Fileargs.Length < 2)
        {
            dataFile = @"text.txt";
            signedFile = "signedFile.enc";

            if (!File.Exists(dataFile))
            {
                // Create a file to write to.
                using (StreamWriter sw = File.CreateText(dataFile))
                {
                    sw.WriteLine("Here is a message to sign");
                }
            }
        }
        else
        {
            dataFile = Fileargs[0];
            signedFile = Fileargs[1];
        }
        try
        {
            // Create a random key using a random number generator. This would be the
            //  secret key shared by sender and receiver.
            byte[] secretkey = new Byte[64];
            //RNGCryptoServiceProvider is an implementation of a random number generator.
            using (RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider())
            {
                // The array is now filled with cryptographically strong random bytes.
                rng.GetBytes(secretkey);

                // Use the secret key to sign the message file.
                SignFile(secretkey, dataFile, signedFile);

                // Verify the signed file
                VerifyFile(secretkey, signedFile);
            }
        }
        catch (IOException e)
        {
            Console.WriteLine("Error: File not found", e);
        }
    }  //end main
    // Computes a keyed hash for a source file and creates a target file with the keyed hash
    // prepended to the contents of the source file.
    public static void SignFile(byte[] key, String sourceFile, String destFile)
    {
        // Initialize the keyed hash object.
        using (HMACSHA256 hmac = new HMACSHA256(key))
        {
            using (FileStream inStream = new FileStream(sourceFile, FileMode.Open))
            {
                using (FileStream outStream = new FileStream(destFile, FileMode.Create))
                {
                    // Compute the hash of the input file.
                    byte[] hashValue = hmac.ComputeHash(inStream);
                    // Reset inStream to the beginning of the file.
                    inStream.Position = 0;
                    // Write the computed hash value to the output file.
                    outStream.Write(hashValue, 0, hashValue.Length);
                    // Copy the contents of the sourceFile to the destFile.
                    int bytesRead;
                    // read 1K at a time
                    byte[] buffer = new byte[1024];
                    do
                    {
                        // Read from the wrapping CryptoStream.
                        bytesRead = inStream.Read(buffer, 0, 1024);
                        outStream.Write(buffer, 0, bytesRead);
                    } while (bytesRead > 0);
                }
            }
        }
        return;
    } // end SignFile

    // Compares the key in the source file with a new key created for the data portion of the file. If the keys
    // compare the data has not been tampered with.
    public static bool VerifyFile(byte[] key, String sourceFile)
    {
        bool err = false;
        // Initialize the keyed hash object.
        using (HMACSHA256 hmac = new HMACSHA256(key))
        {
            // Create an array to hold the keyed hash value read from the file.
            byte[] storedHash = new byte[hmac.HashSize / 8];
            // Create a FileStream for the source file.
            using (FileStream inStream = new FileStream(sourceFile, FileMode.Open))
            {
                // Read in the storedHash.
                inStream.Read(storedHash, 0, storedHash.Length);
                // Compute the hash of the remaining contents of the file.
                // The stream is properly positioned at the beginning of the content,
                // immediately after the stored hash value.
                byte[] computedHash = hmac.ComputeHash(inStream);
                // compare the computed hash with the stored value

                for (int i = 0; i < storedHash.Length; i++)
                {
                    if (computedHash[i] != storedHash[i])
                    {
                        err = true;
                    }
                }
            }
        }
        if (err)
        {
            Console.WriteLine("Hash values differ! Signed file has been tampered with!");
            return false;
        }
        else
        {
            Console.WriteLine("Hash values agree -- no tampering occurred.");
            return true;
        }
    } //end VerifyFile
} //end class
Imports System.IO
Imports System.Security.Cryptography

Public Class HMACSHA256example

    Public Shared Sub Main(ByVal Fileargs() As String)
        Dim dataFile As String
        Dim signedFile As String
        'If no file names are specified, create them.
        If Fileargs.Length < 2 Then
            dataFile = "text.txt"
            signedFile = "signedFile.enc"

            If Not File.Exists(dataFile) Then
                ' Create a file to write to.
                Using sw As StreamWriter = File.CreateText(dataFile)
                    sw.WriteLine("Here is a message to sign")
                End Using
            End If

        Else
            dataFile = Fileargs(0)
            signedFile = Fileargs(1)
        End If
        Try
            ' Create a random key using a random number generator. This would be the
            '  secret key shared by sender and receiver.
            Dim secretkey() As Byte = New [Byte](63) {}
            'RNGCryptoServiceProvider is an implementation of a random number generator.
            Using rng As New RNGCryptoServiceProvider()
                ' The array is now filled with cryptographically strong random bytes.
                rng.GetBytes(secretkey)

                ' Use the secret key to encode the message file.
                SignFile(secretkey, dataFile, signedFile)

                ' Take the encoded file and decode
                VerifyFile(secretkey, signedFile)
            End Using
        Catch e As IOException
            Console.WriteLine("Error: File not found", e)
        End Try

    End Sub

    ' Computes a keyed hash for a source file and creates a target file with the keyed hash
    ' prepended to the contents of the source file. 
    Public Shared Sub SignFile(ByVal key() As Byte, ByVal sourceFile As String, ByVal destFile As String)
        ' Initialize the keyed hash object.
        Using myhmac As New HMACSHA256(key)
            Using inStream As New FileStream(sourceFile, FileMode.Open)
                Using outStream As New FileStream(destFile, FileMode.Create)
                    ' Compute the hash of the input file.
                    Dim hashValue As Byte() = myhmac.ComputeHash(inStream)
                    ' Reset inStream to the beginning of the file.
                    inStream.Position = 0
                    ' Write the computed hash value to the output file.
                    outStream.Write(hashValue, 0, hashValue.Length)
                    ' Copy the contents of the sourceFile to the destFile.
                    Dim bytesRead As Integer
                    ' read 1K at a time
                    Dim buffer(1023) As Byte
                    Do
                        ' Read from the wrapping CryptoStream.
                        bytesRead = inStream.Read(buffer, 0, 1024)
                        outStream.Write(buffer, 0, bytesRead)
                    Loop While bytesRead > 0
                End Using
            End Using
        End Using
        Return

    End Sub
    ' end SignFile

    ' Compares the key in the source file with a new key created for the data portion of the file. If the keys 
    ' compare the data has not been tampered with.
    Public Shared Function VerifyFile(ByVal key() As Byte, ByVal sourceFile As String) As Boolean
        Dim err As Boolean = False
        ' Initialize the keyed hash object. 
        Using hmac As New HMACSHA256(key)
            ' Create an array to hold the keyed hash value read from the file.
            Dim storedHash(hmac.HashSize / 8 - 1) As Byte
            ' Create a FileStream for the source file.
            Using inStream As New FileStream(sourceFile, FileMode.Open)
                ' Read in the storedHash.
                inStream.Read(storedHash, 0, storedHash.Length - 1)
                ' Compute the hash of the remaining contents of the file.
                ' The stream is properly positioned at the beginning of the content, 
                ' immediately after the stored hash value.
                Dim computedHash As Byte() = hmac.ComputeHash(inStream)
                ' compare the computed hash with the stored value
                Dim i As Integer
                For i = 0 To storedHash.Length - 2
                    If computedHash(i) <> storedHash(i) Then
                        err = True
                    End If
                Next i
            End Using
        End Using
        If err Then
            Console.WriteLine("Hash values differ! Signed file has been tampered with!")
            Return False
        Else
            Console.WriteLine("Hash values agree -- no tampering occurred.")
            Return True
        End If

    End Function 'VerifyFile 
End Class
'end class

注解

HMACSHA256 是一种键控哈希算法,它由 SHA-256 哈希函数构造,用作基于哈希的消息身份验证代码 (HMAC) 。 HMAC 进程将密钥与消息数据混合,使用哈希函数对结果进行哈希处理,再次将哈希值与密钥混合,然后再次应用哈希函数。 输出哈希的长度为 256 位。

HMAC 可用于确定通过不安全通道发送的消息是否已被篡改,前提是发送方和接收方共享密钥。 发送方计算原始数据的哈希值,并将原始数据和哈希值作为单个消息发送。 接收方重新计算收到的消息的哈希值,并检查计算的 HMAC 是否与传输的 HMAC 匹配。

对数据或哈希值的任何更改都会导致不匹配,因为需要知道密钥才能更改消息并重现正确的哈希值。 因此,如果原始哈希值和计算的哈希值匹配,则会对消息进行身份验证。

HMACSHA256 接受任何大小的密钥,并生成长度为 256 位的哈希序列。

构造函数

HMACSHA256()

使用随机生成的密钥初始化 HMACSHA256 类的新实例。

HMACSHA256(Byte[])

使用指定的密钥数据初始化 HMACSHA256 类的新实例。

字段

HashSizeInBits

HMAC SHA256 算法生成的哈希大小(以位为单位)。

HashSizeInBytes

HMAC SHA256 算法生成的哈希大小(以字节为单位)。

HashSizeValue

表示计算所得的哈希代码的大小(以位为单位)。

(继承自 HashAlgorithm)
HashValue

表示计算所得的哈希代码的值。

(继承自 HashAlgorithm)
KeyValue

用于哈希算法的密钥。

(继承自 KeyedHashAlgorithm)
State

表示哈希计算的状态。

(继承自 HashAlgorithm)

属性

BlockSizeValue

获取或设置哈希值中使用的块大小。

(继承自 HMAC)
CanReuseTransform

获取一个值,该值指示是否可重复使用当前转换。

(继承自 HashAlgorithm)
CanTransformMultipleBlocks

当在派生类中重写时,获取一个值,该值指示是否可以转换多个块。

(继承自 HashAlgorithm)
Hash

获取计算所得的哈希代码的值。

(继承自 HashAlgorithm)
HashName

获取或设置用于哈希计算的哈希算法的名称。

(继承自 HMAC)
HashSize

获取计算得到的 HMAC 的大小(以位为单位)。

HashSize

获取计算所得的哈希代码的大小(以位为单位)。

(继承自 HashAlgorithm)
InputBlockSize

当在派生类中重写时,获取输入块的大小。

(继承自 HashAlgorithm)
Key

获取或设置要在 HMAC 计算中使用的密钥。

Key

获取或设置要在 HMAC 计算中使用的密钥。

(继承自 HMAC)
OutputBlockSize

当在派生类中重写时,获取输出块的大小。

(继承自 HashAlgorithm)

方法

Clear()

释放 HashAlgorithm 类使用的所有资源。

(继承自 HashAlgorithm)
ComputeHash(Byte[])

计算指定字节数组的哈希值。

(继承自 HashAlgorithm)
ComputeHash(Byte[], Int32, Int32)

计算指定字节数组的指定区域的哈希值。

(继承自 HashAlgorithm)
ComputeHash(Stream)

计算指定 Stream 对象的哈希值。

(继承自 HashAlgorithm)
ComputeHashAsync(Stream, CancellationToken)

异步计算指定 Stream 对象的哈希值。

(继承自 HashAlgorithm)
Dispose()

释放 HashAlgorithm 类的当前实例所使用的所有资源。

(继承自 HashAlgorithm)
Dispose(Boolean)

释放由 HMACSHA256 占用的非托管资源,还可以另外再释放托管资源。

Dispose(Boolean)

密钥更改合法时释放由 HMAC 类使用的非托管资源,并可选择释放托管资源。

(继承自 HMAC)
Equals(Object)

确定指定对象是否等于当前对象。

(继承自 Object)
GetHashCode()

作为默认哈希函数。

(继承自 Object)
GetType()

获取当前实例的 Type

(继承自 Object)
HashCore(Byte[], Int32, Int32)

将写入对象的数据路由到 HMAC 算法以计算 HMAC 。

HashCore(Byte[], Int32, Int32)

在派生类中重写时,将写入对象的数据路由到 HMAC 算法以计算 HMAC 值。

(继承自 HMAC)
HashCore(ReadOnlySpan<Byte>)

将写入对象的数据路由到 HMAC 算法以计算 HMAC 。

HashCore(ReadOnlySpan<Byte>)

将写入对象的数据路由到 HMAC 算法以计算 HMAC 。

(继承自 HMAC)
HashData(Byte[], Byte[])

使用 SHA256 算法计算数据的 HMAC。

HashData(Byte[], Stream)

使用 SHA256 算法计算流的 HMAC。

HashData(ReadOnlySpan<Byte>, ReadOnlySpan<Byte>)

使用 SHA256 算法计算数据的 HMAC。

HashData(ReadOnlySpan<Byte>, ReadOnlySpan<Byte>, Span<Byte>)

使用 SHA256 算法计算数据的 HMAC。

HashData(ReadOnlySpan<Byte>, Stream)

使用 SHA256 算法计算流的 HMAC。

HashData(ReadOnlySpan<Byte>, Stream, Span<Byte>)

使用 SHA256 算法计算流的 HMAC。

HashDataAsync(Byte[], Stream, CancellationToken)

使用 SHA256 算法异步计算流的 HMAC。

HashDataAsync(ReadOnlyMemory<Byte>, Stream, CancellationToken)

使用 SHA256 算法异步计算流的 HMAC。

HashDataAsync(ReadOnlyMemory<Byte>, Stream, Memory<Byte>, CancellationToken)

使用 SHA256 算法异步计算流的 HMAC。

HashFinal()

在算法处理最后一个数据后,结束 HMAC 计算。

HashFinal()

在派生类中重写时,在算法处理最后一个数据后结束 HMAC 计算。

(继承自 HMAC)
Initialize()

将哈希算法重置为其初始状态。

Initialize()

初始化默认 HMAC 实现的实例。

(继承自 HMAC)
MemberwiseClone()

创建当前 Object 的浅表副本。

(继承自 Object)
ToString()

返回表示当前对象的字符串。

(继承自 Object)
TransformBlock(Byte[], Int32, Int32, Byte[], Int32)

计算输入字节数组指定区域的哈希值,并将输入字节数组指定区域复制到输出字节数组的指定区域。

(继承自 HashAlgorithm)
TransformFinalBlock(Byte[], Int32, Int32)

计算指定字节数组的指定区域的哈希值。

(继承自 HashAlgorithm)
TryComputeHash(ReadOnlySpan<Byte>, Span<Byte>, Int32)

尝试计算指定字节数组的哈希值。

(继承自 HashAlgorithm)
TryHashData(ReadOnlySpan<Byte>, ReadOnlySpan<Byte>, Span<Byte>, Int32)

尝试使用 SHA256 算法计算数据的 HMAC。

TryHashFinal(Span<Byte>, Int32)

在 HMAC 算法处理最后一个数据后,尝试结束 HMAC 计算。

TryHashFinal(Span<Byte>, Int32)

在 HMAC 算法处理最后一个数据后,尝试结束 HMAC 计算。

(继承自 HMAC)

显式接口实现

IDisposable.Dispose()

释放由 HashAlgorithm 占用的非托管资源,还可以另外再释放托管资源。

(继承自 HashAlgorithm)

适用于

另请参阅