C# RSA公钥、私钥对格式（XML与PEM）转换器

public static class RsaKeysFormatExtensions
{
/// <summary>
/// XML公钥转成Pem公钥
/// </summary>
/// <param name="xmlPublicKey"></param>
/// <returns></returns>
public static string XmlPublicKeyToPem(this string xmlPublicKey)
{
RSAParameters rsaParam;
using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
{
rsa.FromXmlString(xmlPublicKey);
rsaParam = rsa.ExportParameters(false);
}
RsaKeyParameters param = new RsaKeyParameters(false, new BigInteger(1, rsaParam.Modulus), new BigInteger(1, rsaParam.Exponent));

string pemPublicKeyStr = null;
using (var ms = new MemoryStream())
{
using (var sw = new StreamWriter(ms))
{
var pemWriter = new Org.BouncyCastle.OpenSsl.PemWriter(sw);
pemWriter.WriteObject(param);
sw.Flush();

byte[] buffer = new byte[ms.Length];
ms.Position = 0;
ms.Read(buffer, 0, (int)ms.Length);
pemPublicKeyStr = Encoding.UTF8.GetString(buffer);
}
}

return pemPublicKeyStr;
}

/// <summary>
/// Pem公钥转成XML公钥
/// </summary>
/// <param name="pemPublicKeyStr"></param>
/// <returns></returns>
public static string PemPublicKeyToXml(this string pemPublicKeyStr)
{
RsaKeyParameters pemPublicKey;
using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(pemPublicKeyStr)))
{
using (var sr = new StreamReader(ms))
{
var pemReader = new Org.BouncyCastle.OpenSsl.PemReader(sr);
pemPublicKey = (RsaKeyParameters)pemReader.ReadObject();
}
}

var p = new RSAParameters
{
Modulus = pemPublicKey.Modulus.ToByteArrayUnsigned(),
Exponent = pemPublicKey.Exponent.ToByteArrayUnsigned()
};

string xmlPublicKeyStr;
using (var rsa = new RSACryptoServiceProvider())
{
rsa.ImportParameters(p);
xmlPublicKeyStr = rsa.ToXmlString(false);
}

return xmlPublicKeyStr;
}

/// <summary>
/// XML私钥转成PEM私钥
/// </summary>
/// <param name="xmlPrivateKey"></param>
/// <returns></returns>
public static string XmlPrivateKeyToPem(this string xmlPrivateKey)
{
RSAParameters rsaParam;
using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
{
rsa.FromXmlString(xmlPrivateKey);
rsaParam = rsa.ExportParameters(true);
}

var param = new RsaPrivateCrtKeyParameters(
new BigInteger(1, rsaParam.Modulus), new BigInteger(1, rsaParam.Exponent), new BigInteger(1, rsaParam.D),
new BigInteger(1, rsaParam.P), new BigInteger(1, rsaParam.Q), new BigInteger(1, rsaParam.DP), new BigInteger(1, rsaParam.DQ),
new BigInteger(1, rsaParam.InverseQ));

string pemPrivateKeyStr = null;
using (var ms = new MemoryStream())
{
using (var sw = new StreamWriter(ms))
{
var pemWriter = new Org.BouncyCastle.OpenSsl.PemWriter(sw);
pemWriter.WriteObject(param);
sw.Flush();

byte[] buffer = new byte[ms.Length];
ms.Position = 0;
ms.Read(buffer, 0, (int)ms.Length);
pemPrivateKeyStr = Encoding.UTF8.GetString(buffer);
}
}

return pemPrivateKeyStr;
}

/// <summary>
/// Pem私钥转成XML私钥
/// </summary>
/// <param name="pemPrivateKeyStr"></param>
/// <returns></returns>
public static string PemPrivateKeyToXml(this string pemPrivateKeyStr)
{
RsaPrivateCrtKeyParameters pemPrivateKey;
using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(pemPrivateKeyStr)))
{
using (var sr = new StreamReader(ms))
{
var pemReader = new Org.BouncyCastle.OpenSsl.PemReader(sr);
var keyPair = (AsymmetricCipherKeyPair)pemReader.ReadObject();
pemPrivateKey = (RsaPrivateCrtKeyParameters)keyPair.Private;
}
}

var p = new RSAParameters
{
Modulus = pemPrivateKey.Modulus.ToByteArrayUnsigned(),
Exponent = pemPrivateKey.PublicExponent.ToByteArrayUnsigned(),
D = pemPrivateKey.Exponent.ToByteArrayUnsigned(),
P = pemPrivateKey.P.ToByteArrayUnsigned(),
Q = pemPrivateKey.Q.ToByteArrayUnsigned(),
DP = pemPrivateKey.DP.ToByteArrayUnsigned(),
DQ = pemPrivateKey.DQ.ToByteArrayUnsigned(),
InverseQ = pemPrivateKey.QInv.ToByteArrayUnsigned(),
};

string xmlPrivateKeyStr;
using (var rsa = new RSACryptoServiceProvider())
{
rsa.ImportParameters(p);
xmlPrivateKeyStr = rsa.ToXmlString(true);
}

return xmlPrivateKeyStr;
}

}