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RSACryptoServiceProvider.SignData Method

Computes the hash value of the specified data and signs it.

Overload List

Computes the hash value of the specified byte array using the specified hash algorithm, and signs the resulting hash value.

[Visual Basic] Overloads Public Function SignData(Byte(), Object) As Byte()
[C#] public byte[] SignData(byte[], object);
[C++] public: unsigned char SignData(unsigned char __gc[], Object*) __gc[];
[JScript] public function SignData(Byte[], Object) : Byte[];

Computes the hash value of the specified input stream using the specified hash algorithm, and signs the resulting hash value.

[Visual Basic] Overloads Public Function SignData(Stream, Object) As Byte()
[C#] public byte[] SignData(Stream, object);
[C++] public: unsigned char SignData(Stream*, Object*) __gc[];
[JScript] public function SignData(Stream, Object) : Byte[];

Computes the hash value of a subset of the specified byte array using the specified hash algorithm, and signs the resulting hash value.

[Visual Basic] Overloads Public Function SignData(Byte(), Integer, Integer, Object) As Byte()
[C#] public byte[] SignData(byte[], int, int, object);
[C++] public: unsigned char SignData(unsigned char __gc[], int, int, Object*) __gc[];
[JScript] public function SignData(Byte[], int, int, Object) : Byte[];

Example

[Visual Basic, C#] The following example shows how to use the SignData method.

[Visual Basic, C#] Note   This example shows how to use one of the overloaded versions of SignData. For other examples that might be available, see the individual overload topics.
[Visual Basic] 
Imports System.Security.Cryptography
Imports System.Text

Module RSACSPExample

    Sub Main()
        Try
            ' Create a UnicodeEncoder to convert between byte array and string.
            Dim ByteConverter As New ASCIIEncoding

            Dim dataString As String = "Data to Sign"

            ' Create byte arrays to hold original, encrypted, and decrypted data.
            Dim originalData As Byte() = ByteConverter.GetBytes(dataString)
            Dim signedData() As Byte
            Dim smallArray() As Byte

            ' Create a new instance of the RSACryptoServiceProvider class 
            ' and automatically create a new key-pair.
            Dim RSAalg As New RSACryptoServiceProvider

            ' Export the key information to an RSAParameters object.
            ' You must pass true to export the private key for signing.
            ' However, you do not need to export the private key
            ' for verification.
            Dim Key As RSAParameters = RSAalg.ExportParameters(True)

            ' Hash and sign the data.  Start at the fifth offset
            ' only use data from the next 7 bytes.
            signedData = HashAndSignBytes(originalData, Key, 5, 7)

            ' The previous function only signed one segment
            ' of the array.  Create a new array for verification
            ' that only holds the data that was actually signed.
            '
            ' Initialize the array.
            smallArray = New Byte(6) {}
            ' Copy 7 bytes starting at the 5th index to 
            ' the new array.
            Array.Copy(originalData, 5, smallArray, 0, 7)

            ' Verify the data and display the result to the 
            ' console.  
            If VerifySignedHash(smallArray, signedData, Key) Then
                Console.WriteLine("The data was verified.")
            Else
                Console.WriteLine("The data does not match the signature.")
            End If

        Catch e As ArgumentNullException
            Console.WriteLine("The data was not signed or verified")
        End Try
    End Sub

    Function HashAndSignBytes(ByVal DataToSign() As Byte, ByVal Key As RSAParameters, ByVal Index As Integer, ByVal Length As Integer) As Byte()
        Try
            ' Create a new instance of RSACryptoServiceProvider using the 
            ' key from RSAParameters.  
            Dim RSAalg As New RSACryptoServiceProvider

            RSAalg.ImportParameters(Key)

            ' Hash and sign the data. Pass a new instance of SHA1CryptoServiceProvider
            ' to specify the use of SHA1 for hashing.
            Return RSAalg.SignData(DataToSign, Index, Length, New SHA1CryptoServiceProvider)
        Catch e As CryptographicException
            Console.WriteLine(e.Message)

            Return Nothing
        End Try
    End Function


    Function VerifySignedHash(ByVal DataToVerify() As Byte, ByVal SignedData() As Byte, ByVal Key As RSAParameters) As Boolean
        Try
            ' Create a new instance of RSACryptoServiceProvider using the 
            ' key from RSAParameters.
            Dim RSAalg As New RSACryptoServiceProvider

            RSAalg.ImportParameters(Key)

            ' Verify the data using the signature.  Pass a new instance of SHA1CryptoServiceProvider
            ' to specify the use of SHA1 for hashing.
            Return RSAalg.VerifyData(DataToVerify, New SHA1CryptoServiceProvider, SignedData)

        Catch e As CryptographicException
            Console.WriteLine(e.Message)

            Return False
        End Try
    End Function
End Module

[C#] 
using System;
using System.Security.Cryptography;
using System.Text;

class RSACSPSample
{
    static void Main()
    {
        try
        {
            // Create a UnicodeEncoder to convert between byte array and string.
            ASCIIEncoding ByteConverter = new ASCIIEncoding();

            string dataString = "Data to Sign";

            // Create byte arrays to hold original, encrypted, and decrypted data.
            byte[] originalData = ByteConverter.GetBytes(dataString);
            byte[] signedData;
            byte[] smallArray;

            // Create a new instance of the RSACryptoServiceProvider class 
            // and automatically create a new key-pair.
            RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider();

            // Export the key information to an RSAParameters object.
            // You must pass true to export the private key for signing.
            // However, you do not need to export the private key
            // for verification.
            RSAParameters Key = RSAalg.ExportParameters(true);

            // Hash and sign the data.  Start at the fifth offset
            // only use data from the next 7 bytes.
            signedData = HashAndSignBytes(originalData, Key, 5, 7 );

            // The previous method only signed one segment
            // of the array.  Create a new array for verification
            // that only holds the data that was actually signed.
            //
            // Initialize the array.
            smallArray = new byte[7];
            // Copy 7 bytes starting at the 5th index to 
            // the new array.
            Array.Copy(originalData, 5 , smallArray, 0, 7); 

            // Verify the data and display the result to the 
            // console.  
            if(VerifySignedHash(smallArray, signedData, Key))
            {
                Console.WriteLine("The data was verified.");
            }
            else
            {
                Console.WriteLine("The data does not match the signature.");
            }

        }
        catch(ArgumentNullException)
        {
            Console.WriteLine("The data was not signed or verified");

        }
    }
    public static byte[] HashAndSignBytes(byte[] DataToSign, RSAParameters Key, int Index, int Length)
    {
        try
        {   
            // Create a new instance of RSACryptoServiceProvider using the 
            // key from RSAParameters.  
            RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider();

            RSAalg.ImportParameters(Key);

            // Hash and sign the data. Pass a new instance of SHA1CryptoServiceProvider
            // to specify the use of SHA1 for hashing.
            return RSAalg.SignData(DataToSign,Index,Length, new SHA1CryptoServiceProvider());
        }
        catch(CryptographicException e)
        {
            Console.WriteLine(e.Message);

            return null;
        }
    }

    public static bool VerifySignedHash(byte[] DataToVerify, byte[] SignedData, RSAParameters Key)
    {
        try
        {
            // Create a new instance of RSACryptoServiceProvider using the 
            // key from RSAParameters.
            RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider();

            RSAalg.ImportParameters(Key);

            // Verify the data using the signature.  Pass a new instance of SHA1CryptoServiceProvider
            // to specify the use of SHA1 for hashing.
            return RSAalg.VerifyData(DataToVerify, new SHA1CryptoServiceProvider(), SignedData); 

        }
        catch(CryptographicException e)
        {
            Console.WriteLine(e.Message);

            return false;
        }
    }
}

[C++, JScript] No example is available for C++ or JScript. To view a Visual Basic or C# example, click the Language Filter button Language Filter in the upper-left corner of the page.

See Also

RSACryptoServiceProvider Class | RSACryptoServiceProvider Members | System.Security.Cryptography Namespace

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