如何将RSACryptoServiceProvider私钥导入弹力城堡

Question

目前，我正在使用etoken（safenet），充气城堡库和X509certificate2来解密p7m文件。

我想使用X509Ceritificate2私钥通过Bouncy Castle库解密p7m byteArray。我可以从X509Store检索X509Ceritificate2私钥，密钥不为空。当它是RSACryptoServiceProvider对象时，我可以使用私钥。

RSACryptoServiceProvider systemUserOnlyReadablePrivateKey = certificate.PrivateKey as RSACryptoServiceProvider;

但是，当我尝试将私钥从RSACryptoServiceProvider对象转换为其他对象（如byte []或AsymetricKeyParameter）时，异常消息“密钥无效，无法在指定状态下使用”。已被证明。

AsymetricKeyParameter key = DotNetUtilities.GetKeyPair(cert.Privat‌​eKey).Private; //Exception prompt

由于证书存储在eToken中并在eToken插件插入计算机时自动添加到X509Store中，并且在eToken插件时删除了证书，因此我无法将证书设置为可导出。

1. Bouncy Castle API是否支持使用X509Ceritificate2私钥进行解密？
2. 如何将密钥转换为其他对象，以便我可以通过Bouncy Castle API进行解密。

感谢。

以下是我的源代码。

byte[] p7mByte = p7mByteArray; //p7m to byte array

cmsEnvelopedData = new CmsEnvelopedDataParser(p7mByteArray);
RecipientInformationStore recipientInformationStore = cmsEnvelopedData.GetRecipientInfos();

RecipientInformation recipientInformation = null;

X509Store store = new X509Store(StoreName.My, StoreLocation.CurrentUser);
store.Open(OpenFlags.MaxAllowed);
var certificates = store.Certificates;

foreach (var certificate in certificates)
{
  if (certificate.PrivateKey != null)
  {
     RecipientID recipientId = new RecipientID();
     recipientId.SerialNumber = certificate.SerialNumber;
     recipientId.Issuer = certificate.IssuerDN;
     recipientInformation = recipientInformationStore.GetFirstRecipient(recipientId);

     RSACryptoServiceProvider systemUserOnlyReadablePrivateKey = certificate.PrivateKey as RSACryptoServiceProvider;
     CspParameters cspParameters = new CspParameters(systemUserOnlyReadablePrivateKey.CspKeyContainerInfo.ProviderType, systemUserOnlyReadablePrivateKey.CspKeyContainerInfo.ProviderName, systemUserOnlyReadablePrivateKey.CspKeyContainerInfo.KeyContainerName)
     {
        Flags = CspProviderFlags.UseArchivableKey 
     };

     RSACryptoServiceProvider csp = new RSACryptoServiceProvider(cspParameters);
     csp = (RSACryptoServiceProvider)certificate.PrivateKey;

     CmsTypedStream recData = null;
     recData = recipientInformation.GetContentStream(DotNetUtilities.GetKeyPair(cert.Privat‌​eKey).Private); //Exception prompt
  }
}