how can sign a file with BouncyCastle dll in c#

Question

I starting with BouncyCastle Crypto dll and I'n not found enought documentation. I need one example of how can I sign a file with different alghoritms Like sha1 sha256 and other and obtain .p7m file. Can somebody help to me ? Many thanks in advance Piercarlo

Answer 1

I put together this little example for you:

using System;
using System.IO;
using System.Linq;
using System.Windows.Forms;
using Org.BouncyCastle.Cms;
using Org.BouncyCastle.Pkcs;
using Org.BouncyCastle.X509;

namespace ConsoleApplicationSignWithBouncyCastle
{
    class Program
    {

        [STAThread]
        static void Main(string[] args)
        {

            try
            {
                // First load a Certificate, filename/path and certificate password
                Cert = ReadCertFromFile("./test.pfx", "test");

                //  Select a binary file
                var dialog = new OpenFileDialog
                                 {
                                     Filter = "All files (*.*)|*.*",
                                     InitialDirectory = "./",
                                     Title = "Select a text file"
                                 };
                var filename = (dialog.ShowDialog() == DialogResult.OK) ? dialog.FileName : null;

                // Get the file
                var f = new FileStream(filename, System.IO.FileMode.Open);

                // Reading through this code stub to be sure I get it all :-)  [ Different subject entirely ]
                var fileContent = ReadFully(f);

                // Create the generator
                var dataGenerator = new CmsEnvelopedDataStreamGenerator();

                // Add receiver
                // Cert is the user's X.509 Certificate set bellow
                dataGenerator.AddKeyTransRecipient(Cert);

                // Make the output stream
                var outStream = new FileStream(filename + ".p7m", FileMode.Create);

                // Sign the stream
                var cryptoStream = dataGenerator.Open(outStream, CmsEnvelopedGenerator.Aes128Cbc);

                // Store in our binary stream writer and write the signed content
                var binWriter = new BinaryWriter(cryptoStream);
                binWriter.Write(fileContent);
            }
            catch (Exception ex)
            {
                Console.WriteLine("So, you wanna make an exception huh! : " + ex.ToString());
                Console.ReadKey();
            }
        }

        public static byte[] ReadFully(Stream stream)
        {
            stream.Seek(0, 0);
            var buffer = new byte[32768];
            using (var ms = new MemoryStream())
            {
                while (true)
                {
                    int read = stream.Read(buffer, 0, buffer.Length);
                    if (read <= 0)
                        return ms.ToArray();
                    ms.Write(buffer, 0, read);
                }
            }
        }

        public static Org.BouncyCastle.X509.X509Certificate Cert { get; set; }

        // This reads a certificate from a file.
        // Thanks to: http://blog.softwarecodehelp.com/2009/06/23/CodeForRetrievePublicKeyFromCertificateAndEncryptUsingCertificatePublicKeyForBothJavaC.aspx
        public static X509Certificate ReadCertFromFile(string strCertificatePath, string strCertificatePassword)
        {
            try
            {
                // Create file stream object to read certificate
                var keyStream = new FileStream(strCertificatePath, FileMode.Open, FileAccess.Read);

                // Read certificate using BouncyCastle component
                var inputKeyStore = new Pkcs12Store();
                inputKeyStore.Load(keyStream, strCertificatePassword.ToCharArray());

                //Close File stream
                keyStream.Close();

                var keyAlias = inputKeyStore.Aliases.Cast<string>().FirstOrDefault(n => inputKeyStore.IsKeyEntry(n));

                // Read Key from Alieases  
                if (keyAlias == null)
                    throw new NotImplementedException("Alias");

                //Read certificate into 509 format
                return (X509Certificate)inputKeyStore.GetCertificate(keyAlias).Certificate;
            }
            catch (Exception ex)
            {
                Console.WriteLine("So, you wanna make an exception huh! : " + ex.ToString());
            Console.ReadKey();
            return null;
        }
    }
} }

Hope this helps.

I also posted it on my blog.