How to Create Digital Signature and Verify it in C# using PKCS 7 and SHA algorithm

Question

I am trying to digitally sign xml document and verify the signature with the original xml file with public key and signed document. I have a java code for reference. I need to convert java code to C# where I have java code like this:

   certList = new ArrayList<X509Certificate>();
   certList.add(signerCert);
   certStore = new JcaCertStore(certList);
   signedDataGenerator = new CMSSignedDataGenerator();
   ContentSigner sha2Signer = new JcaContentSignerBuilder("SHA512with" + privateKey.getAlgorithm()).build(privateKey);

   ignedDataGenerator.addSignerInfoGenerator(new JcaSignerInfoGeneratorBuilder(new JcaDigestCalculatorProviderBuilder().build()).setDirectSignature(true).build(sha2Signer, signerCert));
   signedDataGenerator.addCertificates(certStore);
   CMSSignedData sigData = signedDataGenerator.generate(new CMSProcessableFile(inputXmlFile), false);
   signedBytes = sigData.getEncoded();

I have converted java code to C# like this:

        X509Store my = new X509Store(StoreName.My, StoreLocation.LocalMachine);
        my.Open(OpenFlags.ReadOnly);
        // Find the certificate we’ll use to sign
        RSACryptoServiceProvider csp = null;
        foreach (X509Certificate2 cert in my.Certificates)
        {
            if (cert.Subject.Contains(certSubject))
            {
                // We found it.
                // Get its associated CSP and private key
                csp = (RSACryptoServiceProvider)cert.PrivateKey;                  
            }
        }
        if (csp == null)
        {
            throw new Exception("oppose no valid application was found");
        }
        // Hash the data
        SHA512Managed sha1 = new SHA512Managed();
        UnicodeEncoding encoding = new UnicodeEncoding();
        byte[] data = encoding.GetBytes(text);
        byte[] hash = sha1.ComputeHash(data);
        // Sign the hash
        return csp.SignHash(hash, CryptoConfig.MapNameToOID("SHA1"));

I am trying to convert it since two days, It is generating sign byte array but not been able to verify. While verifying it is throwing bad hash\r\n error I shall be highly grateful for any assistance. I know I am somewhere wrong in converting the java code to C#. I am able to verify the code but not been able to sign the document

Welcome to Stack Overflow! Questions seeking debugging help ("why isn't this code working?") must include the desired behavior, _a specific problem or error_ and _the shortest code necessary_ to reproduce it **in the question itself**. Questions without a clear problem statement are not useful to other readers. See: [How to create a Minimal, Complete, and Verifiable example](http://stackoverflow.com/help/mcve). — Joe C, Jul 03 '17 at 07:26

score 2 · Accepted Answer · answered Jul 03 '17 at 11:21

I have generated Signature using System.Security.Cryptography.Pkcs library like this

    public static byte[] Sign(byte[] data, X509Certificate2 certificate)
    {
        if (data == null)
            throw new ArgumentNullException("data");
        if (certificate == null)
            throw new ArgumentNullException("certificate");

        // setup the data to sign
        ContentInfo content = new ContentInfo(data);
        SignedCms signedCms = new SignedCms(content, false);
        CmsSigner signer = new CmsSigner(SubjectIdentifierType.IssuerAndSerialNumber, certificate);
        // create the signature
        signedCms.ComputeSignature(signer);
        return signedCms.Encode();
    }

and verify the signature like this

  private static bool VerifySignatures(FileInfo contentFile, Stream signedDataStream)
    {
        CmsProcessable signedContent = null;
        CmsSignedData cmsSignedData = null;
        Org.BouncyCastle.X509.Store.IX509Store store = null;
        ICollection signers = null;
        bool verifiedStatus = false;
        try
        {
            //Org.BouncyCastle.Security.addProvider(new BouncyCastleProvider());
            signedContent = new CmsProcessableFile(contentFile);
            cmsSignedData = new CmsSignedData(signedContent, signedDataStream);
            store = cmsSignedData.GetCertificates("Collection");//.getCertificates();
            IX509Store certStore = cmsSignedData.GetCertificates("Collection");
            signers = cmsSignedData.GetSignerInfos().GetSigners();
            foreach (var item in signers)
            {
                SignerInformation signer = (SignerInformation)item;
                var certCollection = certStore.GetMatches(signer.SignerID);
                IEnumerator iter = certCollection.GetEnumerator();
                iter.MoveNext();
                var cert = (Org.BouncyCastle.X509.X509Certificate)iter.Current;
                verifiedStatus = signer.Verify(cert.GetPublicKey());
            }

        }
        catch (Exception e)
        {
            throw e;
        }

        return verifiedStatus;
    }

It is working for me

Question what exactly is signedDataStream and where do you get it from and how? Thx — Naruto, Mar 17 '20 at 18:51

How to Create Digital Signature and Verify it in C# using PKCS 7 and SHA algorithm

1 Answers1