Certificate Signing Request (CSR) Generation Code Sample

The following code sample generates a CSR with the BouncyCastle C# library.

Note: This is not a complete sample and does not securely store the private key. This is only for illustration purposes.

var keyPair = GenerateKeyPair();
var keyPem = new StringBuilder();
var keyPemWriter = new PemWriter(new StringWriter(keyPem));
keyPemWriter.WriteObject(keyPair.Public);
keyPemWriter.Writer.Flush();

var transportKey = RemovePemHeaderFooter(keyPem.ToString());
var csrData = GenerateCertRequest(keyPair);

public static AsymmetricCipherKeyPair GenerateKeyPair()
{
 // Generate private/public key pair
 RsaKeyPairGenerator generator = new RsaKeyPairGenerator();
 KeyGenerationParameters keyParams = new KeyGenerationParameters(new SecureRandom(), 2048);
 generator.Init(keyParams);
 return generator.GenerateKeyPair();
}

private static string RemovePemHeaderFooter(string input)
{
 var headerFooterList = new List\<string\>()
 {
 "-----BEGIN CERTIFICATE REQUEST-----",
 "-----END CERTIFICATE REQUEST-----",
 "-----BEGIN PUBLIC KEY-----",
 "-----END PUBLIC KEY-----",
 "-----BEGIN RSA PRIVATE KEY-----",
 "-----END RSA PRIVATE KEY-----"
 };

 string trimmed = input;
 foreach (var hf in headerFooterList)
 {
 trimmed = trimmed.Replace(hf, string.Empty);
 }

 return trimmed.Replace("\r\n", string.Empty);
}

private static string GenerateCertRequest(AsymmetricCipherKeyPair keyPair)
{
 var values = new Dictionary<DerObjectIdentifier, string> {
 {X509Name.CN, "Microsoft"}, //domain name inside the quotes
 {X509Name.O, "Microsoft Corp"}, //Organisation\'s Legal name inside the quotes
 {X509Name.L, "Redmond"},
 {X509Name.ST, "Washington"},
 {X509Name.C, "US"},
 };

 var subject = new X509Name(values.Keys.Reverse().ToList(), values);
 var csr = new Pkcs10CertificationRequest(
 new Asn1SignatureFactory("SHA256withRSA", keyPair.Private),
 subject,
 keyPair.Public,
 null,
 keyPair.Private);

 //Convert BouncyCastle csr to PEM format
 var csrPem = new StringBuilder();
 var csrPemWriter = new PemWriter(new StringWriter(csrPem));
 csrPemWriter.WriteObject(csr);
 csrPemWriter.Writer.Flush();
 return RemovePemHeaderFooter(csrPem.ToString());
}