RSACryptoServiceProvider.SignData Method (Byte[], Object)

 

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

Namespace:   System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)

public byte[] SignData(
	byte[] buffer,
	object halg
)

Parameters

buffer
Type: System.Byte[]

The input data for which to compute the hash.

halg
Type: System.Object

The hash algorithm to use to create the hash value.

Return Value

Type: System.Byte[]

The RSA signature for the specified data.

Exception Condition
ArgumentNullException

The halg parameter is null.

ArgumentException

The halg parameter is not a valid type.

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

The halg parameter can accept a String, a HashAlgorithm, or a Type.

The following code example signs and verifies data.

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;

            // 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.
            signedData = HashAndSignBytes(originalData, Key);

            // Verify the data and display the result to the 
            // console.
            if(VerifySignedHash(originalData, 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)
    {
        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, 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;
        }
    }
}

.NET Framework
Available since 1.1
Windows Phone Silverlight
Available since 7.1
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