Using CngKey to generate an RSA key pair in PEM (DKIM compatible) using C # .... similar to "openssl rsa"

Question

Is it possible to create an RSA key pair, export it to ASN1 format, compatible with DKIM PEM format, using only C #?

I would like to reduce my dependencies on third parties, but here are some of them that I found

Bouncy castle

• stack overflow

Cryptography Application Block

• http://msdn.microsoft.com/en-us/library/dd203099.aspx
• stack overflow

Win32 PFXImportCertStore

• http://msdn.microsoft.com/en-us/library/aa387314(v=vs.85).aspx
• http://msdn.microsoft.com/en-us/library/aa387313(v=vs.85)

Import PEM

• This code only imports PEM data, but differs from OpenSSL in that it fixes a problem with .NET 4.0 and leading zeros in the key http://www.codeproject.com/Articles/162194/Certificates-to-DB-and-Back

Microsoft CLR Security Enhancements

• http://clrsecurity.codeplex.com/

Microsoft CNG

• http://msdn.microsoft.com/en-us/magazine/cc163389.aspx

Here is the code for Microsoft CNG provider with .NET dll on codeplex (above) ... however, I don’t know how to export and import both public and private keys into DKIM compatible ASN1 format .

byte[] pkcs8PrivateKey = null; byte[] signedData = null; CngKey key = CngKey.Create(CngAlgorithm2.Rsa); byte[] exportedPrivateBytes = key.Export(CngKeyBlobFormat.GenericPrivateBlob); string exportedPrivateString= Encoding.UTF8.GetString(exportedPrivateBytes); pkcs8PrivateKey = Encoding.UTF8.GetBytes(exportedPrivateString); using (CngKey signingKey = CngKey.Import(pkcs8PrivateKey, CngKeyBlobFormat.Pkcs8PrivateBlob)) { using (RSACng rsa = new RSACng(signingKey)) { rsa.SignatureHashAlgorithm = CngAlgorithm.Sha1; signedData = rsa.SignData(dataToSign); } } 

Question

Are there any direct examples of using Microsoft libraries (Win32, PFX, or CLR on Codeplex) that illustrate how to create a key pair and export / import these values ​​in PEM format?

Answer 1

So you just need the pkcs8 key.

 CngKeyCreationParameters ckcParams = new CngKeyCreationParameters() { ExportPolicy = CngExportPolicies.AllowExportPlainText, KeyCreationOptions = CngKeyCreationOptions.None, KeyUsage = CngKeyUsages.AllUsages, }; ckcParams.Parameters.Add(new CngProperty("Length", BitConverter.GetBytes(2048), CngPropertyOptions.None)); myCngKey = CngKey.Create(CngAlgorithm.Rsa, null, ckcParams); byte[] privatePlainTextBlob = myCngKey.Export(CngKeyBlobFormat.Pkcs8PrivateBlob); Console.WriteLine(Convert.ToBase64String(privatePlainTextBlob)); } 

Your key pair is now contained in the PKCS # 8 ASN.1 encoded string.