DSACryptoServiceProvider Class
Updated: May 2009
Defines a wrapper object to access the cryptographic service provider (CSP) implementation of the DSA algorithm. This class cannot be inherited.
Assembly: mscorlib (in mscorlib.dll)
You can use the DSACryptoServiceProvider class to create digital signatures and protect the integrity of your data.
To use a public-key system to digitally sign a message, the sender first applies a hash function to the message to create a message digest. The sender then encrypts the message digest with the sender's private key to create the sender's personal signature. Upon receiving the message and signature, the receiver decrypts the signature using the sender's public key to recover the message digest and hashes the message using the same hash algorithm that the sender used. If the message digest that the receiver computes exactly matches the message digest received from the sender, the receiver can be sure that the message was not altered while in transit. Note that a signature can be verified by anyone, because the sender's public key is common knowledge.
This algorithm supports key lengths from 512 bits to 1024 bits in increments of 64 bits.
Important Note: |
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You should ensure that IDisposable is called when you are finished with the DSACryptoServiceProvider. To do this, instantiate the object in a using statement; for example, using (DSACryptoServiceProvider DSA = new DSACryptoServiceProvider()). For more information about the using statement, see using Statement (C# Reference) or Using Statement (Visual Basic). |
The following code example creates a digital signature of a hash value using the DSACryptoServiceProvider class and then verifies the signature.
Imports System Imports System.Security.Cryptography Public Class DSACSPSample Public Shared Sub Main() Try Dim privateKeyInfo As DSAParameters Dim publicKeyInfo As DSAParameters ' Create a new instance of DSACryptoServiceProvider to generate ' a new key pair. Using DSA As New DSACryptoServiceProvider() privateKeyInfo = DSA.ExportParameters(True) publicKeyInfo = DSA.ExportParameters(False) End Using ' The hash value to sign. Dim HashValue As Byte() = _ { 59, 4, 248, 102, 77, 97, 142, 201, 210, 12, 224, _ 93, 25, 41, 100, 197, 213, 134, 130, 135} 'The value to hold the signed value. Dim SignedHashValue As Byte() = DSASignHash(HashValue, privateKeyInfo, "SHA1") ' Verify the hash and display the results. Dim verified As Boolean = DSAVerifyHash(HashValue, SignedHashValue, publicKeyInfo, "SHA1") If verified Then Console.WriteLine("The hash value was verified.") Else Console.WriteLine("The hash value was not verified.") End If Catch e As ArgumentNullException Console.WriteLine(e.Message) End Try End Sub Public Shared Function DSASignHash(HashToSign As Byte(), DSAKeyInfo As DSAParameters, _ HashAlg As String) As Byte() Dim sig As Byte() = Nothing Try ' Create a new instance of DSACryptoServiceProvider. Using DSA As New DSACryptoServiceProvider() 'Import the key information. DSA.ImportParameters(DSAKeyInfo) ' Create an DSASignatureFormatter object and pass it the ' DSACryptoServiceProvider to transfer the private key. Dim DSAFormatter As New DSASignatureFormatter(DSA) ' Set the hash algorithm to the passed value. DSAFormatter.SetHashAlgorithm(HashAlg) ' Create a signature for HashValue and return it. sig = DSAFormatter.CreateSignature(HashToSign) End Using Catch e As CryptographicException Console.WriteLine(e.Message) End Try Return sig End Function Public Shared Function DSAVerifyHash(HashValue As Byte(), SignedHashValue As Byte(), _ DSAKeyInfo As DSAParameters, HashAlg As String) As Boolean Dim verified As Boolean = False Try ' Create a new instance of DSACryptoServiceProvider. Using DSA As New DSACryptoServiceProvider() ' Import the key information. DSA.ImportParameters(DSAKeyInfo) ' Create an DSASignatureDeformatter object and pass it the ' DSACryptoServiceProvider to transfer the private key. Dim DSADeformatter As New DSASignatureDeformatter(DSA) ' Set the hash algorithm to the passed value. DSADeformatter.SetHashAlgorithm(HashAlg) ' Verify signature and return the result. verified = DSADeformatter.VerifySignature(HashValue, SignedHashValue) End Using Catch e As CryptographicException Console.WriteLine(e.Message) End Try Return verified End Function End Class
System.Security.Cryptography.AsymmetricAlgorithm
System.Security.Cryptography.DSA
System.Security.Cryptography.DSACryptoServiceProvider
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Date | History | Reason |
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May 2009 | Added a note about ensuring that IDisposable is called after you use this class. | Information enhancement. |
Important Note: