RSACryptoServiceProvider.SignHash RSACryptoServiceProvider.SignHash RSACryptoServiceProvider.SignHash RSACryptoServiceProvider.SignHash Method

Definition

Computes the signature for the specified hash value by encrypting it with the private key.

Overloads

SignHash(Byte[], String) SignHash(Byte[], String) SignHash(Byte[], String) SignHash(Byte[], String)

Computes the signature for the specified hash value by encrypting it with the private key.

SignHash(Byte[], HashAlgorithmName, RSASignaturePadding) SignHash(Byte[], HashAlgorithmName, RSASignaturePadding) SignHash(Byte[], HashAlgorithmName, RSASignaturePadding) SignHash(Byte[], HashAlgorithmName, RSASignaturePadding)

Computes the signature for the specified hash value by encrypting it with the private key using the specified padding.

SignHash(Byte[], String) SignHash(Byte[], String) SignHash(Byte[], String) SignHash(Byte[], String)

Computes the signature for the specified hash value by encrypting it with the private key.

public:
 cli::array <System::Byte> ^ SignHash(cli::array <System::Byte> ^ rgbHash, System::String ^ str);
public byte[] SignHash (byte[] rgbHash, string str);
member this.SignHash : byte[] * string -> byte[]
Public Function SignHash (rgbHash As Byte(), str As String) As Byte()

Parameters

rgbHash
Byte[]

The hash value of the data to be signed.

str
String String String String

The hash algorithm identifier (OID) used to create the hash value of the data.

Returns

Byte[]

The RSA signature for the specified hash value.

Exceptions

The cryptographic service provider (CSP) cannot be acquired.

-or-

There is no private key.

Examples

The following code example encrypts some data, creates a hash of the encrypted data, and then signs hash with a digital signature.

#using <System.dll>

using namespace System;
using namespace System::Text;
using namespace System::Security::Cryptography;
ref class Sender
{
private:
   RSAParameters rsaPubParams;
   RSAParameters rsaPrivateParams;

public:
   Sender()
   {
      RSACryptoServiceProvider^ rsaCSP = gcnew RSACryptoServiceProvider;
      
      //Generate public and private key data.
      rsaPrivateParams = rsaCSP->ExportParameters( true );
      rsaPubParams = rsaCSP->ExportParameters( false );
   }


   property RSAParameters PublicParameters 
   {
      RSAParameters get()
      {
         return rsaPubParams;
      }

   }

   //Manually performs hash and then signs hashed value.
   array<Byte>^ HashAndSign( array<Byte>^encrypted )
   {
      RSACryptoServiceProvider^ rsaCSP = gcnew RSACryptoServiceProvider;
      SHA1Managed^ hash = gcnew SHA1Managed;
      array<Byte>^hashedData;
      rsaCSP->ImportParameters( rsaPrivateParams );
      hashedData = hash->ComputeHash( encrypted );
      return rsaCSP->SignHash( hashedData, CryptoConfig::MapNameToOID( "SHA1" ) );
   }


   //Encrypts using only the public key data.
   array<Byte>^ EncryptData( RSAParameters rsaParams, array<Byte>^toEncrypt )
   {
      RSACryptoServiceProvider^ rsaCSP = gcnew RSACryptoServiceProvider;
      rsaCSP->ImportParameters( rsaParams );
      return rsaCSP->Encrypt( toEncrypt, false );
   }

};

ref class Receiver
{
private:
   RSAParameters rsaPubParams;
   RSAParameters rsaPrivateParams;

public:
   Receiver()
   {
      RSACryptoServiceProvider^ rsaCSP = gcnew RSACryptoServiceProvider;
      
      //Generate public and private key data.
      rsaPrivateParams = rsaCSP->ExportParameters( true );
      rsaPubParams = rsaCSP->ExportParameters( false );
   }


   property RSAParameters PublicParameters 
   {
      RSAParameters get()
      {
         return rsaPubParams;
      }

   }

   //Manually performs hash and then verifies hashed value.
   bool VerifyHash( RSAParameters rsaParams, array<Byte>^signedData, array<Byte>^signature )
   {
      RSACryptoServiceProvider^ rsaCSP = gcnew RSACryptoServiceProvider;
      SHA1Managed^ hash = gcnew SHA1Managed;
      array<Byte>^hashedData;
      rsaCSP->ImportParameters( rsaParams );
      bool dataOK = rsaCSP->VerifyData(signedData, CryptoConfig::MapNameToOID("SHA1"), signature);
      hashedData = hash->ComputeHash( signedData );
      return rsaCSP->VerifyHash( hashedData, CryptoConfig::MapNameToOID( "SHA1" ), signature );
   }


   //Decrypt using the private key data.
   void DecryptData( array<Byte>^encrypted )
   {
      array<Byte>^fromEncrypt;
      String^ roundTrip;
      ASCIIEncoding^ myAscii = gcnew ASCIIEncoding;
      RSACryptoServiceProvider^ rsaCSP = gcnew RSACryptoServiceProvider;
      rsaCSP->ImportParameters( rsaPrivateParams );
      fromEncrypt = rsaCSP->Decrypt( encrypted, false );
      roundTrip = myAscii->GetString( fromEncrypt );
      Console::WriteLine( "RoundTrip: {0}", roundTrip );
   }

};

int main()
{
   array<Byte>^toEncrypt;
   array<Byte>^encrypted;
   array<Byte>^signature;
   
   //Choose a small amount of data to encrypt.
   String^ original = "Hello";
   ASCIIEncoding^ myAscii = gcnew ASCIIEncoding;
   
   //Create a sender and receiver.
   Sender^ mySender = gcnew Sender;
   Receiver^ myReceiver = gcnew Receiver;
   
   //Convert the data string to a byte array.
   toEncrypt = myAscii->GetBytes( original );
   
   //Encrypt data using receiver's public key.
   encrypted = mySender->EncryptData( myReceiver->PublicParameters, toEncrypt );
   
   //Hash the encrypted data and generate a signature on the hash
   // using the sender's private key.
   signature = mySender->HashAndSign( encrypted );
   Console::WriteLine( "Original: {0}", original );
   
   //Verify the signature is authentic using the sender's public key.
   if ( myReceiver->VerifyHash( mySender->PublicParameters, encrypted, signature ) )
   {
      
      //Decrypt the data using the receiver's private key.
      myReceiver->DecryptData( encrypted );
   }
   else
   {
      Console::WriteLine( "Invalid signature" );
   }
}

using System;
using System.Text;
using System.Security.Cryptography;

namespace RSACryptoServiceProvider_Examples
{
    class MyMainClass
    {
        static void Main()
        {
            byte[] toEncrypt;
            byte[] encrypted;
            byte[] signature;
            //Choose a small amount of data to encrypt.
            string original = "Hello";
            ASCIIEncoding myAscii = new ASCIIEncoding();

            //Create a sender and receiver.
            Sender mySender = new Sender();
            Receiver myReceiver = new Receiver();

            //Convert the data string to a byte array.
            toEncrypt = myAscii.GetBytes(original);

            //Encrypt data using receiver's public key.
            encrypted = mySender.EncryptData(myReceiver.PublicParameters, toEncrypt);

            //Hash the encrypted data and generate a signature on the hash
            // using the sender's private key.
            signature = mySender.HashAndSign(encrypted);

            Console.WriteLine("Original: {0}", original);

            //Verify the signature is authentic using the sender's public key.
            if (myReceiver.VerifyHash(mySender.PublicParameters, encrypted, signature))
            {
                //Decrypt the data using the receiver's private key.
                myReceiver.DecryptData(encrypted);
            }
            else
            {
                Console.WriteLine("Invalid signature");
            }
        }
    }

    class Sender
    {
        RSAParameters rsaPubParams;
        RSAParameters rsaPrivateParams;

        public Sender()
        {
            RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider();

            //Generate public and private key data.
            rsaPrivateParams = rsaCSP.ExportParameters(true);
            rsaPubParams = rsaCSP.ExportParameters(false);
        }

        public RSAParameters PublicParameters
        {
            get
            {
                return rsaPubParams;
            }
        }

        //Manually performs hash and then signs hashed value.
        public byte[] HashAndSign(byte[] encrypted)
        {
            RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider();
            SHA1Managed hash = new SHA1Managed();
            byte[] hashedData;

            rsaCSP.ImportParameters(rsaPrivateParams);

            hashedData = hash.ComputeHash(encrypted);
            return rsaCSP.SignHash(hashedData, CryptoConfig.MapNameToOID("SHA1"));
        }

        //Encrypts using only the public key data.
        public byte[] EncryptData(RSAParameters rsaParams, byte[] toEncrypt)
        {
            RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider();

            rsaCSP.ImportParameters(rsaParams);
            return rsaCSP.Encrypt(toEncrypt, false);
        }
    }

    class Receiver
    {
        RSAParameters rsaPubParams;
        RSAParameters rsaPrivateParams;

        public Receiver()
        {
            RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider();

            //Generate public and private key data.
            rsaPrivateParams = rsaCSP.ExportParameters(true);
            rsaPubParams = rsaCSP.ExportParameters(false);
        }

        public RSAParameters PublicParameters
        {
            get
            {
                return rsaPubParams;
            }
        }

        //Manually performs hash and then verifies hashed value.
        public bool VerifyHash(RSAParameters rsaParams, byte[] signedData, byte[] signature)
        {
            RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider();
            SHA1Managed hash = new SHA1Managed();
            byte[] hashedData;

            rsaCSP.ImportParameters(rsaParams);
            bool dataOK = rsaCSP.VerifyData(signedData, CryptoConfig.MapNameToOID("SHA1"), signature);
            hashedData = hash.ComputeHash(signedData);
            return rsaCSP.VerifyHash(hashedData, CryptoConfig.MapNameToOID("SHA1"), signature);
        }

        //Decrypt using the private key data.
        public void DecryptData(byte[] encrypted)
        {
            byte[] fromEncrypt;
            string roundTrip;
            ASCIIEncoding myAscii = new ASCIIEncoding();
            RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider();

            rsaCSP.ImportParameters(rsaPrivateParams);
            fromEncrypt = rsaCSP.Decrypt(encrypted, false);
            roundTrip = myAscii.GetString(fromEncrypt);

            Console.WriteLine("RoundTrip: {0}", roundTrip);
        }
    }
}
Imports System.Text
Imports System.Security.Cryptography

Namespace RSACryptoServiceProvider_Examples
    Class MyMainClass
        Shared Sub Main()
            Dim toEncrypt() As Byte
            Dim encrypted() As Byte
            Dim signature() As Byte
            'Choose a small amount of data to encrypt.
            Dim original As String = "Hello"
            Dim myAscii As New ASCIIEncoding()

            'Create a sender and receiver.
            Dim mySender As New Sender()
            Dim myReceiver As New Receiver()

            'Convert the data string to a byte array.
            toEncrypt = myAscii.GetBytes(original)

            'Encrypt data using receiver's public key.
            encrypted = mySender.EncryptData(myReceiver.PublicParameters, toEncrypt)

            'Hash the encrypted data and generate a signature on the hash
            ' using the sender's private key.
            signature = mySender.HashAndSign(encrypted)

            Console.WriteLine("Original: {0}", original)

            'Verify the signature is authentic using the sender's public key.
            If myReceiver.VerifyHash(mySender.PublicParameters, encrypted, signature) Then
                'Decrypt the data using the receiver's private key.
                myReceiver.DecryptData(encrypted)
            Else
                Console.WriteLine("Invalid signature")
            End If
        End Sub
    End Class

    Class Sender
        Private rsaPubParams As RSAParameters
        Private rsaPrivateParams As RSAParameters

        Public Sub New()
            Dim rsaCSP As New RSACryptoServiceProvider()

            'Generate public and private key data.
            rsaPrivateParams = rsaCSP.ExportParameters(True)
            rsaPubParams = rsaCSP.ExportParameters(False)
        End Sub

        Public ReadOnly Property PublicParameters() As RSAParameters
            Get
                Return rsaPubParams
            End Get
        End Property

        'Manually performs hash and then signs hashed value.
        Public Function HashAndSign(ByVal encrypted() As Byte) As Byte()
            Dim rsaCSP As New RSACryptoServiceProvider()
            Dim hash As New SHA1Managed()
            Dim hashedData() As Byte

            rsaCSP.ImportParameters(rsaPrivateParams)

            hashedData = hash.ComputeHash(encrypted)
            Return rsaCSP.SignHash(hashedData, CryptoConfig.MapNameToOID("SHA1"))
        End Function 'HashAndSign

        'Encrypts using only the public key data.
        Public Function EncryptData(ByVal rsaParams As RSAParameters, ByVal toEncrypt() As Byte) As Byte()
            Dim rsaCSP As New RSACryptoServiceProvider()

            rsaCSP.ImportParameters(rsaParams)
            Return rsaCSP.Encrypt(toEncrypt, False)
        End Function 'EncryptData
    End Class

    Class Receiver
        Private rsaPubParams As RSAParameters
        Private rsaPrivateParams As RSAParameters

        Public Sub New()
            Dim rsaCSP As New RSACryptoServiceProvider()

            'Generate public and private key data.
            rsaPrivateParams = rsaCSP.ExportParameters(True)
            rsaPubParams = rsaCSP.ExportParameters(False)
        End Sub

        Public ReadOnly Property PublicParameters() As RSAParameters
            Get
                Return rsaPubParams
            End Get
        End Property

        'Manually performs hash and then verifies hashed value.
        Public Function VerifyHash(ByVal rsaParams As RSAParameters, ByVal signedData() As Byte, ByVal signature() As Byte) As Boolean
            Dim rsaCSP As New RSACryptoServiceProvider()
            Dim hash As New SHA1Managed()
            Dim hashedData() As Byte
            Dim dataOK As Boolean

            rsaCSP.ImportParameters(rsaParams)
            dataOK = rsaCSP.VerifyData(signedData, CryptoConfig.MapNameToOID("SHA1"), signature)
            hashedData = hash.ComputeHash(signedData)
            Return rsaCSP.VerifyHash(hashedData, CryptoConfig.MapNameToOID("SHA1"), signature)
        End Function 'VerifyHash

        'Decrypt using the private key data.
        Public Sub DecryptData(ByVal encrypted() As Byte)
            Dim fromEncrypt() As Byte
            Dim roundTrip As String
            Dim myAscii As New ASCIIEncoding()
            Dim rsaCSP As New RSACryptoServiceProvider()

            rsaCSP.ImportParameters(rsaPrivateParams)
            fromEncrypt = rsaCSP.Decrypt(encrypted, False)
            roundTrip = myAscii.GetString(fromEncrypt)

            Console.WriteLine("RoundTrip: {0}", roundTrip)
        End Sub
    End Class
End Namespace 'RSACryptoServiceProvider_Examples

Remarks

This method creates a digital signature that is verified using the VerifyHash method.

The valid hash algorithms are SHA1 and MD5. The algorithm identifier can be derived from the hash name by using the MapNameToOID method.

Due to collision problems with SHA1 and MD5, Microsoft recommends a security model based on SHA256 or better.

Security

KeyContainerPermissionAccessEntryCollection
for permission to sign a file using the key. Security action: Demand. Associated enumeration: Sign

See also

SignHash(Byte[], HashAlgorithmName, RSASignaturePadding) SignHash(Byte[], HashAlgorithmName, RSASignaturePadding) SignHash(Byte[], HashAlgorithmName, RSASignaturePadding) SignHash(Byte[], HashAlgorithmName, RSASignaturePadding)

Computes the signature for the specified hash value by encrypting it with the private key using the specified padding.

public:
 override cli::array <System::Byte> ^ SignHash(cli::array <System::Byte> ^ hash, System::Security::Cryptography::HashAlgorithmName hashAlgorithm, System::Security::Cryptography::RSASignaturePadding ^ padding);
public override byte[] SignHash (byte[] hash, System.Security.Cryptography.HashAlgorithmName hashAlgorithm, System.Security.Cryptography.RSASignaturePadding padding);
override this.SignHash : byte[] * System.Security.Cryptography.HashAlgorithmName * System.Security.Cryptography.RSASignaturePadding -> byte[]
Public Overrides Function SignHash (hash As Byte(), hashAlgorithm As HashAlgorithmName, padding As RSASignaturePadding) As Byte()

Parameters

hash
Byte[]

The hash value of the data to be signed.

hashAlgorithm
HashAlgorithmName HashAlgorithmName HashAlgorithmName HashAlgorithmName

The hash algorithm name used to create the hash value of the data.

Returns

Byte[]

The RSA signature for the specified hash value.

Exceptions

Applies to