C# 将私有/公共 RSA 密钥从 RSACryptoServiceProvider 导出到 PEM 字符串
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【中文标题】C# 将私有/公共 RSA 密钥从 RSACryptoServiceProvider 导出到 PEM 字符串【英文标题】：C# Export Private/Public RSA key from RSACryptoServiceProvider to PEM string 【发布时间】：2014-07-07 05:44:07 【问题描述】：我有一个 System.Security.Cryptography.RSACryptoServiceProvider 实例，我需要将它的密钥导出到 PEM 字符串 - 像这样：
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----
但是根据 MSDN 文档没有这样的选项，只有某种 XML 导出。我不能使用像 BouncyCastle 这样的第三方库。 有没有办法生成这个字符串？
【问题讨论】：
该类的实例如何以及在何处拥有密钥？ 痛点是由于 .Net 及其使用来自RFC 3275 的 XML 编码。 .Net 不使用 ASN.1/DER 或 PEM 编码的密钥。我认为它是唯一一个以这种方式做事的加密库。 【参考方案1】：请注意：以下代码用于导出 private 密钥。如果您希望导出 public 密钥，请参考我给出的答案here。
PEM 格式只是将密钥的ASN.1DER 编码（每个PKCS#1）转换为 Base64。鉴于表示密钥所需的字段数量有限，创建快速而肮脏的 DER 编码器以输出适当的格式然后进行 Base64 编码非常简单。因此，下面的代码不是特别优雅，但可以完成工作：
private static void ExportPrivateKey(RSACryptoServiceProvider csp, TextWriter outputStream)
if (csp.PublicOnly) throw new ArgumentException("CSP does not contain a private key", "csp");
var parameters = csp.ExportParameters(true);
using (var stream = new MemoryStream())
var writer = new BinaryWriter(stream);
writer.Write((byte)0x30); // SEQUENCE
using (var innerStream = new MemoryStream())
var innerWriter = new BinaryWriter(innerStream);
EncodeIntegerBigEndian(innerWriter, new byte[] 0x00 ); // Version
EncodeIntegerBigEndian(innerWriter, parameters.Modulus);
EncodeIntegerBigEndian(innerWriter, parameters.Exponent);
EncodeIntegerBigEndian(innerWriter, parameters.D);
EncodeIntegerBigEndian(innerWriter, parameters.P);
EncodeIntegerBigEndian(innerWriter, parameters.Q);
EncodeIntegerBigEndian(innerWriter, parameters.DP);
EncodeIntegerBigEndian(innerWriter, parameters.DQ);
EncodeIntegerBigEndian(innerWriter, parameters.InverseQ);
var length = (int)innerStream.Length;
EncodeLength(writer, length);
writer.Write(innerStream.GetBuffer(), 0, length);
var base64 = Convert.ToBase64String(stream.GetBuffer(), 0, (int)stream.Length).ToCharArray();
outputStream.WriteLine("-----BEGIN RSA PRIVATE KEY-----");
// Output as Base64 with lines chopped at 64 characters
for (var i = 0; i < base64.Length; i += 64)
outputStream.WriteLine(base64, i, Math.Min(64, base64.Length - i));
outputStream.WriteLine("-----END RSA PRIVATE KEY-----");
private static void EncodeLength(BinaryWriter stream, int length)
if (length < 0) throw new ArgumentOutOfRangeException("length", "Length must be non-negative");
if (length < 0x80)
// Short form
stream.Write((byte)length);
else
// Long form
var temp = length;
var bytesRequired = 0;
while (temp > 0)
temp >>= 8;
bytesRequired++;
stream.Write((byte)(bytesRequired | 0x80));
for (var i = bytesRequired - 1; i >= 0; i--)
stream.Write((byte)(length >> (8 * i) & 0xff));
private static void EncodeIntegerBigEndian(BinaryWriter stream, byte[] value, bool forceUnsigned = true)
stream.Write((byte)0x02); // INTEGER
var prefixZeros = 0;
for (var i = 0; i < value.Length; i++)
if (value[i] != 0) break;
prefixZeros++;
if (value.Length - prefixZeros == 0)
EncodeLength(stream, 1);
stream.Write((byte)0);
else
if (forceUnsigned && value[prefixZeros] > 0x7f)
// Add a prefix zero to force unsigned if the MSB is 1
EncodeLength(stream, value.Length - prefixZeros + 1);
stream.Write((byte)0);
else
EncodeLength(stream, value.Length - prefixZeros);
for (var i = prefixZeros; i < value.Length; i++)
stream.Write(value[i]);
【讨论】：
很好，这很完美，但是我如何导出公钥。有没有类似的结构。我尝试仅使用指数和模数（公钥的内容）来执行此操作，但它没有返回有效结果。如何获取公钥字符串？ 没关系。我得到它的工作，我忘了删除版本部分。现在它还导出公钥。 对于那些感兴趣的人，可以通过我的答案中的代码来正确导出公钥：***.com/questions/28406888/…，它重复使用了这个答案中的一些方法。 这非常适合将私钥和公钥导出到pem 文件
我已经编译并稍微修改了 Iridium 的两个出色的导出函数，并将它们与导入函数相结合以获得完整的解决方案（导入和导出公钥和私钥）：Import and export RSA Keys between C# and PEM format using BouncyCastle【参考方案2】：
要导出PublicKey，请使用以下代码：
public static String ExportPublicKeyToPEMFormat(RSACryptoServiceProvider csp)
TextWriter outputStream = new StringWriter();
var parameters = csp.ExportParameters(false);
using (var stream = new MemoryStream())
var writer = new BinaryWriter(stream);
writer.Write((byte)0x30); // SEQUENCE
using (var innerStream = new MemoryStream())
var innerWriter = new BinaryWriter(innerStream);
EncodeIntegerBigEndian(innerWriter, new byte[] 0x00 ); // Version
EncodeIntegerBigEndian(innerWriter, parameters.Modulus);
EncodeIntegerBigEndian(innerWriter, parameters.Exponent);
//All Parameter Must Have Value so Set Other Parameter Value Whit Invalid Data (for keeping Key Structure use "parameters.Exponent" value for invalid data)
EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.D
EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.P
EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.Q
EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.DP
EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.DQ
EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.InverseQ
var length = (int)innerStream.Length;
EncodeLength(writer, length);
writer.Write(innerStream.GetBuffer(), 0, length);
var base64 = Convert.ToBase64String(stream.GetBuffer(), 0, (int)stream.Length).ToCharArray();
outputStream.WriteLine("-----BEGIN PUBLIC KEY-----");
// Output as Base64 with lines chopped at 64 characters
for (var i = 0; i < base64.Length; i += 64)
outputStream.WriteLine(base64, i, Math.Min(64, base64.Length - i));
outputStream.WriteLine("-----END PUBLIC KEY-----");
return outputStream.ToString();
private static void EncodeIntegerBigEndian(BinaryWriter stream, byte[] value, bool forceUnsigned = true)
stream.Write((byte)0x02); // INTEGER
var prefixZeros = 0;
for (var i = 0; i < value.Length; i++)
if (value[i] != 0) break;
prefixZeros++;
if (value.Length - prefixZeros == 0)
EncodeLength(stream, 1);
stream.Write((byte)0);
else
if (forceUnsigned && value[prefixZeros] > 0x7f)
// Add a prefix zero to force unsigned if the MSB is 1
EncodeLength(stream, value.Length - prefixZeros + 1);
stream.Write((byte)0);
else
EncodeLength(stream, value.Length - prefixZeros);
for (var i = prefixZeros; i < value.Length; i++)
stream.Write(value[i]);
private static void EncodeLength(BinaryWriter stream, int length)
if (length < 0) throw new ArgumentOutOfRangeException("length", "Length must be non-negative");
if (length < 0x80)
// Short form
stream.Write((byte)length);
else
// Long form
var temp = length;
var bytesRequired = 0;
while (temp > 0)
temp >>= 8;
bytesRequired++;
stream.Write((byte)(bytesRequired | 0x80));
for (var i = bytesRequired - 1; i >= 0; i--)
stream.Write((byte)(length >> (8 * i) & 0xff));
【讨论】：
我必须删除EncodeIntegerBigEndian(innerWriter, new byte[] 0x00 ); // Version 行才能将生成的 PEM 文件加载到 Poco 库的 Crypto::RSAKey 中。
这对我不起作用。相反，我使用了@Iridium 的另一篇帖子***.com/questions/28406888/…，根据他的答案下方的cmets。
这六个额外的写入到底是什么... RSA 公钥是n,e 对。您应该检查 PKCS #1 以了解网络上的正确格式，而不是像上面那样分享黑客。【参考方案3】：
对于那些对原始答案的明显复杂性犹豫不决的其他人（这非常有帮助，不要误会我的意思），我想我会发布我的解决方案，它更简单一点 IMO（但仍基于原始答案）：
public class RsaCsp2DerConverter
private const int MaximumLineLength = 64;
// Based roughly on: http://***.com/a/23739932/1254575
public RsaCsp2DerConverter()
public byte[] ExportPrivateKey(String cspBase64Blob)
if (String.IsNullOrEmpty(cspBase64Blob) == true)
throw new ArgumentNullException(nameof(cspBase64Blob));
var csp = new RSACryptoServiceProvider();
csp.ImportCspBlob(Convert.FromBase64String(cspBase64Blob));
if (csp.PublicOnly)
throw new ArgumentException("CSP does not contain a private key!", nameof(csp));
var parameters = csp.ExportParameters(true);
var list = new List<byte[]>
new byte[] 0x00,
parameters.Modulus,
parameters.Exponent,
parameters.D,
parameters.P,
parameters.Q,
parameters.DP,
parameters.DQ,
parameters.InverseQ
;
return SerializeList(list);
private byte[] Encode(byte[] inBytes, bool useTypeOctet = true)
int length = inBytes.Length;
var bytes = new List<byte>();
if (useTypeOctet == true)
bytes.Add(0x02); // INTEGER
bytes.Add(0x84); // Long format, 4 bytes
bytes.AddRange(BitConverter.GetBytes(length).Reverse());
bytes.AddRange(inBytes);
return bytes.ToArray();
public String PemEncode(byte[] bytes)
if (bytes == null)
throw new ArgumentNullException(nameof(bytes));
var base64 = Convert.ToBase64String(bytes);
StringBuilder b = new StringBuilder();
b.Append("-----BEGIN RSA PRIVATE KEY-----\n");
for (int i = 0; i < base64.Length; i += MaximumLineLength)
b.Append($" base64.Substring(i, Math.Min(MaximumLineLength, base64.Length - i)) \n");
b.Append("-----END RSA PRIVATE KEY-----\n");
return b.ToString();
private byte[] SerializeList(List<byte[]> list)
if (list == null)
throw new ArgumentNullException(nameof(list));
var keyBytes = list.Select(e => Encode(e)).SelectMany(e => e).ToArray();
var binaryWriter = new BinaryWriter(new MemoryStream());
binaryWriter.Write((byte) 0x30); // SEQUENCE
binaryWriter.Write(Encode(keyBytes, false));
binaryWriter.Flush();
var result = ((MemoryStream) binaryWriter.BaseStream).ToArray();
binaryWriter.BaseStream.Dispose();
binaryWriter.Dispose();
return result;
【讨论】：
【参考方案4】： public static Func<string, string> ToBase64PemFromKeyXMLString= (xmlPrivateKey) =>
if (string.IsNullOrEmpty(xmlPrivateKey))
throw new ArgumentNullException("RSA key must contains value!");
var keyContent = new PemReader(new StringReader(xmlPrivateKey));
if (keyContent == null)
throw new ArgumentNullException("private key is not valid!");
var ciphrPrivateKey = (AsymmetricCipherKeyPair)keyContent.ReadObject();
var asymmetricKey = new AsymmetricKeyEntry(ciphrPrivateKey.Private);
PrivateKeyInfo privateKeyInfo = PrivateKeyInfoFactory.CreatePrivateKeyInfo(asymmetricKey.Key);
var serializedPrivateKey = privateKeyInfo.ToAsn1Object().GetDerEncoded();
return Convert.ToBase64String(serializedPrivateKey);
;
【讨论】：
【参考方案5】：如果您使用的是 .NET Core 3.0，并且您不需要依赖于 Windows 平台的RSACryptoServiceProvider，这已经实现了开箱即用
public string ExportPrivateKey(RSA rsa)
var privateKeyBytes = rsa.ExportRSAPrivateKey();
var builder = new StringBuilder("-----BEGIN RSA PRIVATE KEY");
builder.AppendLine("-----");
var base64PrivateKeyString = Convert.ToBase64String(privateKeyBytes);
var offset = 0;
const int LINE_LENGTH = 64;
while (offset < base64PrivateKeyString.Length)
var lineEnd = Math.Min(offset + LINE_LENGTH, base64PrivateKeyString.Length);
builder.AppendLine(base64PrivateKeyString.Substring(offset, lineEnd - offset));
offset = lineEnd;
builder.Append("-----END RSA PRIVATE KEY");
builder.AppendLine("-----");
return builder.ToString();
注意：在 .NET Core 中，您不会使用 RSACryptoServiceProvider，因为它更特定于 Windows。
【讨论】：
这段代码对我来说工作得很好-但有一个小错误：开头行声明“BEGIN RSA PRIVATE KEY”（这是正确的），但结尾行省略了“RSA”->结束行应该是“END RSA PRIVATE KEY” 嗨@Prasanth，您能否分享一下 .NET Core 中的 RSACryptoServiceProvider 是特定于 Windows 的地方的详细信息？【参考方案6】：使用当前版本的 .NET CORE，无需在所有其他响应中提供所有方便的东西即可完成此操作。
RSA rsa = RSA.Create();
rsa.KeySize = 4096;
string hdr = "-----BEGIN RSA PRIVATE KEY-----";
string ftr = "-----END RSA PRIVATE KEY-----";
string priv = Convert.ToBase64String(rsa.ExportPkcs8PrivateKey());
// To export the public key, update hdr and ftr with `PUBLIC`.
// string pub = Convert.ToBase64String(rsa.ExportSubjectPublicKeyInfo());
string PEM = $"hdr\npriv\nftr";
// Distribute PEM.
【讨论】：
在您对导出公钥的评论中，您说要使用 hdr 和 ftr，但这些值特定于私钥....应该是 hdr="-----BEGIN RSA PUBLIC KEY- ----" and ftr="-----END RSA PUBLIC KEY-----" 也许我写得不好，但说update hdr and ftr in 的意思正是你所说的。 :)以上是关于C# 将私有/公共 RSA 密钥从 RSACryptoServiceProvider 导出到 PEM 字符串的主要内容，如果未能解决你的问题，请参考以下文章