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c#cryptographypki

C# CX509PrivateKey Format

I'm trying to re-use the key pair I generated for creating a PKCS10 Certificate Signing request, but I cannot figure out what the format of this private key is.

To create the key, I'm using the CERTENROLLLib CX509PrivateKey class.

I've set the Private Key ProviderType to XCV_PROV_RSA_FULL, and when I export it (trying to figure out what format it is) I use 

Export("PRIVATEBLOB", EncodingType.XCN_CRYPT_STRING_BASE64)

When I export it, the private key always starts with "BwIAAACkAABSU0E"

Does anyone know what format this is? I thought ANS.1 DER Encoding always started with "MII" or someting like that.

Solution

  • I think I answered my own question:

    The command

    Export("PRIVATEBLOB", EncodingType.XCN_CRYPT_STRING_BASE64)

    exports the private key as a BASE64 encoded CSP blob. In order to import is using the C# RSA libraries I had to use the following:

    RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
byte[] CryptoKey = Convert.FromBase64String(base64CspBlob);
rsa.ImportCspBlob(CryptoKey);

    That did it!