HMACSHA1-Konstruktor ()
Initialisiert eine neue Instanz der HMACSHA1-Klasse mit einem nach dem Zufallsprinzip generierten Schlüssel.
Namespace: System.Security.Cryptography
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Sub New
'Usage
Dim instance As New HMACSHA1
public HMACSHA1 ()
public:
HMACSHA1 ()
public HMACSHA1 ()
public function HMACSHA1 ()
Hinweise
HMACSHA1 ist ein schlüsselgebundener Hashalgorithmus, der von der SHA1-Hashfunktion erstellt und als HMAC verwendet wird, oder ein Hash-Nachrichtenauthentifizierungscode. Der HMAC-Prozess umfasst folgende Schritte: Ein geheimer Schlüssel wird mit den Nachrichtendaten vermischt, für das Ergebnis wird mithilfe der Hashfunktion ein Hash erstellt, der Hashwert wird wiederum mit dem geheimen Schlüssel vermischt, und die Hashfunktion wird ein weiteres Mal angewendet. Der Ausgabehash hat eine Länge von 160 Bits (20 Bytes).
Mit diesem Konstruktor wird ein zufällig generierter 64-Byte-Schlüssel verwendet.
Beispiel
Im folgenden Codebeispiel werden das Codieren einer Datei mithilfe von HMACSHA1 und das anschließende Decodieren der Datei veranschaulicht.
using System;
using System.IO;
using System.Security.Cryptography;
public class HMACSHA1example
{
// 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 decrypts the file and compares
// the source and the decrypted files.
public static void EncodeFile(byte[] key, String sourceFile, String destFile)
{
// Initialize the keyed hash object.
HMACSHA1 myhmacsha1 = new HMACSHA1(key);
FileStream inStream = new FileStream(sourceFile, FileMode.Open);
FileStream outStream = new FileStream(destFile, FileMode.Create);
// Compute the hash of the input file.
byte[] hashValue = myhmacsha1.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);
myhmacsha1.Clear();
// Close the streams
inStream.Close();
outStream.Close();
return;
} // end EncodeFile
// Decrypt the encoded file and compare to original file.
public static bool DecodeFile(byte[] key, String sourceFile)
{
// Initialize the keyed hash object.
HMACSHA1 hmacsha1 = new HMACSHA1(key);
// Create an array to hold the keyed hash value read from the file.
byte[] storedHash = new byte[hmacsha1.HashSize/8];
// Create a FileStream for the source file.
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 = hmacsha1.ComputeHash(inStream);
// compare the computed hash with the stored value
for (int i =0; i < storedHash.Length; i++)
{
if (computedHash[i] != storedHash[i])
{
Console.WriteLine("Hash values differ! Encoded file has been tampered with!");
return false;
}
}
Console.WriteLine("Hash values agree -- no tampering occurred.");
return true;
} //end DecodeFile
private const string usageText = "Usage: HMACSHA1 inputfile.txt encryptedfile.hsh\nYou must specify the two file names. Only the first file must exist.\n";
public static void Main(string[] Fileargs)
{
//If no file names are specified, write usage text.
if (Fileargs.Length < 2)
{
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.
byte[] secretkey = new Byte[64];
//RNGCryptoServiceProvider is an implementation of a random number generator.
RNGCryptoServiceProvider rng = new 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[0], Fileargs[1]);
// Take the encoded file and decode
DecodeFile(secretkey, Fileargs[1]);
}
catch (IOException e)
{
Console.WriteLine("Error: File not found",e);
}
} //end if-else
} //end main
} //end class
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 decrypts the file and compares
// the source and the decrypted files.
void EncodeFile( array<Byte>^key, String^ sourceFile, String^ destFile )
{
// Initialize the keyed hash object.
HMACSHA1^ myhmacsha1 = gcnew HMACSHA1( 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 = myhmacsha1->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 );
myhmacsha1->Clear();
// Close the streams
inStream->Close();
outStream->Close();
return;
} // end EncodeFile
// Decrypt the encoded file and compare to original file.
bool DecodeFile( array<Byte>^key, String^ sourceFile )
{
// Initialize the keyed hash object.
HMACSHA1^ hmacsha1 = gcnew HMACSHA1( key );
// Create an array to hold the keyed hash value read from the file.
array<Byte>^storedHash = gcnew array<Byte>(hmacsha1->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 = hmacsha1->ComputeHash( inStream );
// compare the computed hash with the stored value
for ( int i = 0; i < storedHash->Length; i++ )
{
if ( computedHash[ i ] != storedHash[ i ] )
{
Console::WriteLine( "Hash values differ! Encoded file has been tampered with!" );
return false;
}
}
Console::WriteLine( "Hash values agree -- no tampering occurred." );
return true;
} //end DecodeFile
int main()
{
array<String^>^Fileargs = Environment::GetCommandLineArgs();
String^ usageText = "Usage: HMACSHA1 inputfile.txt encryptedfile.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
import System.*;
import System.IO.*;
import System.Security.Cryptography.*;
public class HMACSHA1Example
{
// 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 decrypts
// the file and compares the source and the decrypted files.
public static void EncodeFile(ubyte key[], String sourceFile,
String destFile)
{
// Initialize the keyed hash object.
HMACSHA1 myhmacsha1 = new HMACSHA1(key);
FileStream inStream = new FileStream(sourceFile, FileMode.Open);
FileStream outStream = new FileStream(destFile, FileMode.Create);
// Compute the hash of the input file.
ubyte hashValue[] = myhmacsha1.ComputeHash(inStream);
// Reset inStream to the beginning of the file.
inStream.set_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
ubyte buffer[] = new ubyte[1024];
do {
// Read from the wrapping CryptoStream.
bytesRead = inStream.Read(buffer, 0, 1024);
outStream.Write(buffer, 0, bytesRead);
} while (bytesRead > 0);
myhmacsha1.Clear();
// Close the streams
inStream.Close();
outStream.Close();
return;
} // end EncodeFile
// Decrypt the encoded file and compare to original file.
public static boolean DecodeFile(ubyte key[], String sourceFile)
{
// Initialize the keyed hash object.
HMACSHA1 hmacsha1 = new HMACSHA1(key);
// Create an array to hold the keyed hash value read from the file.
ubyte storedHash[] = new ubyte[hmacsha1.get_HashSize() / 8];
// Create a FileStream for the source file.
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.
ubyte computedHash[] = hmacsha1.ComputeHash(inStream);
// compare the computed hash with the stored value
for (int i = 0; i < storedHash.length; i++) {
if (computedHash.get_Item(i) != storedHash.get_Item(i)) {
Console.WriteLine("Hash values differ! Encoded file has been "
+ " tampered with!");
return false;
}
}
Console.WriteLine("Hash values agree -- no tampering occurred.");
return true;
} //DecodeFile //end DecodeFile
private static String usageText = "Usage: HMACSHA1 inputfile.txt "
+ "encryptedfile.hsh\nYou must specify the two file names. Only "
+ "the first file must exist.\n";
public static void main(String[] fileargs)
{
//If no file names are specified, write usage text.
if (fileargs.length < 2) {
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.
ubyte secretKey[] = new ubyte[64];
// RNGCryptoServiceProvider is an implementation of a random
// number generator.
RNGCryptoServiceProvider rng = new 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[0], fileargs[1]);
// Take the encoded file and decode
DecodeFile(secretKey, fileargs[1]);
}
catch (IOException e) {
Console.WriteLine("Error: File not found", e);
}
}//end if-else
} //end main
} //end class HMACSHA1Example
Plattformen
Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
Siehe auch
Referenz
HMACSHA1-Klasse
HMACSHA1-Member
System.Security.Cryptography-Namespace