How can I change key pair in xml format to PEM format in C#?

Question

I've try to change created key pair in xml format to PEM format. Here is my code.

CspParameters cspParams = new CspParameters();
cspParams.ProviderType = 1;  
cspParams.Flags = CspProviderFlags.UseArchivableKey;
cspParams.KeyNumber = (int)KeyNumber.Exchange;
rsaProvider = new RSACryptoServiceProvider(1024,cspParams);
RSAParameters rsa_params = rsaProvider.ExportParameters(true);
byte[] rsa_export = rsaProvider.ExportCspBlob(true); 

//here I've try to get private key data
string data__ = Convert.ToBase64String(rsa_export);  
FileStream fs = new FileStream(privateKeyFileName, FileMode.CreateNew);

string type = "RSA PRIVATE KEY";
string header = String.Format("-----BEGIN {0}-----\n", type);
string footer = String.Format("\n-----END {0}-----", type);

data__  = header+data__+footer;
byte[] d_ = Encoding.Default.GetBytes(data__); 

//write to file        
fs.Write(d_, 0, d_.Length);
fs.Close();

After I've run it I've got a private key but when I test by using the key to create a certificate using command:

openssl req -new -x509 -key privatekey.pvk -config       
"C:\AppServ\php5\extras\openssl\openssl.cnf" -out myCert.cer -days 365

an error occured

unable to load Private Key
3004:error:0906D064:PEM routines:PEM_read_bio:bad base64 decode:.\crypto\pem\pem_lib.c:756:

Answer 1

Take a look at this blog post: http://pstaev.blogspot.com.es/2010/08/convert-rsa-public-key-from-xml-to-pem.html

Answer 2

Remember that openssl is picky about PEM certificate formatting.

1. The file must contain: -----BEGIN CERTIFICATE----- on a separate line (i.e. it must be terminated with a newline).
2. Each line of "gibberish" must be 64 characters wide.
3. The file must end with: -----END CERTIFICATE----- and also be terminated with a newline.
4. Don't save the cert text with Word. It must be in ASCII.
5. Don't mix DOS and UNIX style line terminations.

So in your case, it appears you are not line wrapping the "gibberish" at 64 characters, and your END tag is missing the newline.

For others out there not writing their own key pairs, here are a few steps you can take to normalize your certificate files on Linux:

1. Run it through dos2unix: # dos2unix cert.pem
2. Run it through fold: # fold -w 64 cert.pem

If you're on Windows, try downloading Cygwin, and you should be able to get these conversion tools.