Read ECC private key PEM into AsymmetricCipherKeyPair c# bouncy castle

Question

I generate an ECC key pair in PEM format using Bouncy Castle using:

var curve = ECNamedCurveTable.GetByName("secp256k1");
var domainParams = new ECDomainParameters(curve.Curve, curve.G, curve.N, curve.H, curve.GetSeed());

var secureRandom = new SecureRandom();
var keyParams = new ECKeyGenerationParameters(domainParams, secureRandom);

var generator = new ECKeyPairGenerator("ECDSA");
generator.Init(keyParams);
AsymmetricCipherKeyPair keyPair = generator.GenerateKeyPair();
TextWriter textWriter = new StringWriter();
PemWriter pemWriter = new PemWriter(textWriter);
pemWriter.WriteObject(keyPair.Private);
pemWriter.Writer.Flush();
string pem_privatekey = textWriter.ToString();

My current ECC private key is:

-----BEGIN EC PRIVATE KEY-----MIIBUQIBAQQgyDHBaj30dcIsS4otdOXR8ue+rZDwHcGEjxwle3H24W6ggeMwgeACAQEwLAYHKoZIzj0BAQIhAP////////////////////////////////////7///wvMEQEIAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABCAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABwRBBHm+Zn753LusVaBilc6HCwcCm/zbLc4o2VnygVsW+BeYSDradyajxGVdpPv8DhEIqP0XtEimhVQZnEfQj/sQ1LgCIQD////////////////////+uq7c5q9IoDu/0l6M0DZBQQIBAaFEA0IABHxw0PK0uEvnF1lwhkLmHUlVtQVUrLp/1EcKzfAm6xOL/I6LtQ9nXPxDNhaxf/rPtk3DkZ5CaO0hLr1trCRrJz8=-----END EC PRIVATE KEY-----

I want to read this pem format private in a bouncy castle ECPrivateKeyParameters or AsymmetricCipherKeyPair format. I am trying the following code. pem is the above private key string.

PemReader pr = new PemReader(new StringReader(pem));
ECPrivateKeyParameters KeyPair = (ECPrivateKeyParameters)pr.ReadObject();

Why this returns null? Please correct me.

Answer 1

pr.ReadObject() returns an AsymmetricCipherKeyPair instance here. This has the properties Private and Public which here returns an ECPrivateKeyParameters and ECPublicKeyParameters instance respectively, i.e. the code should be:

PemReader pr = new PemReader(new StringReader(pem));
AsymmetricCipherKeyPair keyPair = (AsymmetricCipherKeyPair)pr.ReadObject();
ECPrivateKeyParameters privateKeyParams = (ECPrivateKeyParameters)keyPair.Private;
ECPublicKeyParameters publicKeyParams = (ECPublicKeyParameters)keyPair.Public; // for completeness