C# RSA 公钥输出不正确

Posted 2023-02-16

【中文标题】C# RSA 公钥输出不正确

【英文标题】：C# RSA Public Key Output Not Correct

【发布时间】：2015-04-09 00:32:17

【问题描述】：

我目前正在尝试使用 C# 生成和发送公共 RSA 密钥。它应该是 PEM 格式的 2048 位长密钥。我已经使用 OpenSSL 命令成功完成了以下操作（一些输出被缩短）：

$ openssl genrsa 2048 
Generating RSA private key, 2048 bit long modulus
............................................................+++
............................................................+++
e is 65537 (0x10001)
$ openssl rsa -pubout
-----BEGIN RSA PRIVATE KEY-----
MIIEowIBAAKCAQEAy1MoBtENHBhYLgwP5Hw/xRGaBPHonApChBPBYD6fiq/QoLXA
RmyMoOjXHsKrrwysYIujXADM2LZ0MlFvPbBulvciWnZwp9CUQPwsZ8xnmBWlHyru
xTxNSvV+E/6+2gMOn3I4bmOSIaLx2Y7nCuaenREvD7Mn0vgFnP7yaN8/9va4q8Lo
...
...
y5jiKQKBgGAe9DlkYvR6Edr/gzd6HaF4btQZf6idGdmsYRYc2EMHdRM2NVqlvyLc
MR6rYEuViqLN5XWK6ITOlTPrgAuU6Rl4ZpRlS1ZrfjiUS6dzD/jtJJvsYByC7ZoU
NxIzB0r1hj0TIoedu6NqfRyJ6Fx09U5W81xx77T1EBSg4OCH7eyl
-----END RSA PRIVATE KEY-----
writing RSA key
-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAy1MoBtENHBhYLgwP5Hw/
xRGaBPHonApChBPBYD6fiq/QoLXARmyMoOjXHsKrrwysYIujXADM2LZ0MlFvPbBu
lvciWnZwp9CUQPwsZ8xnmBWlHyruxTxNSvV+E/6+2gMOn3I4bmOSIaLx2Y7nCuae
nREvD7Mn0vgFnP7yaN8/9va4q8LoMKlceE5fSYl2QIfC5ZxUtkblbycEWZHLVOkv
+4Iz0ibD8KGo0PaiZl0jmn9yYXFy747xmwVun+Z4czO8Nu+OOVxsQF4hu1pKvTUx
9yHH/vk5Wr0I09VFyt3BT/RkecJbAAWB9/e572T+hhmmJ08wCs29oFa2Cdik9yyE
2QIDAQAB
-----END PUBLIC KEY-----

以下代码是我使用 C# 生成公钥的代码：

// Variables
CspParameters cspParams = null;
RSACryptoServiceProvider rsaProvider = null;
StreamWriter publicKeyFile = null;
string publicKey = "";

try

   // Create a new key pair on target CSP
   cspParams = new CspParameters();
   cspParams.ProviderType = 1; // PROV_RSA_FULL
   cspParams.Flags = CspProviderFlags.CreateEphemeralKey;
   rsaProvider = new RSACryptoServiceProvider(2048, cspParams);

   // Export public key
   result = ExportPublicKeyToPEMFormat(rsaProvider);

catch (Exception ex)

ExportPublicKeyToPEMFormat 可以从这个线程中找到： https://***.com/a/25591659/2383179

我在 C# 中的输出如下所示：

-----BEGIN PUBLIC KEY-----
MIIBKwIBAAKCAQEAzMoaInPQ7nAXGWUY2EEtBcPY/Zvfcqf3Uxr7mFrQaxMjdXYi
DVSPh9XBWJlEhQ9ZGyBMpkWwtkrlDw11g/7pj+u7KTa5nH1ZB8vCrY3TC+YnFXPQ
Nv5dCzW0Lz+HD04rir2+K++XQCroy7G68uE9dtkbqa1U7IEWOvejbX+sgzo5ISHA
vCz2DFBInqYNJWfkM8OvLnRYYQ4f8MbmvDEMyaEYPGfQybXAs5eFksqm9pwR0xh4
Oxg/DkDas93lNIf+g00IesHvHuavRm2GX8jAXhrAoZY7nWQZpqS5kwx1kjSwtYEg
Vq4mHcaKIalMAoILSV9ttgqiJ5KVuKIvQJ7wRwIDAQABAgMBAAECAwEAAQIDAQAB
AgMBAAECAwEAAQIDAQAB
-----END PUBLIC KEY-----

使用 OpenSSL 的正确输出如下所示：

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAy1MoBtENHBhYLgwP5Hw/
xRGaBPHonApChBPBYD6fiq/QoLXARmyMoOjXHsKrrwysYIujXADM2LZ0MlFvPbBu
lvciWnZwp9CUQPwsZ8xnmBWlHyruxTxNSvV+E/6+2gMOn3I4bmOSIaLx2Y7nCuae
nREvD7Mn0vgFnP7yaN8/9va4q8LoMKlceE5fSYl2QIfC5ZxUtkblbycEWZHLVOkv
+4Iz0ibD8KGo0PaiZl0jmn9yYXFy747xmwVun+Z4czO8Nu+OOVxsQF4hu1pKvTUx
9yHH/vk5Wr0I09VFyt3BT/RkecJbAAWB9/e572T+hhmmJ08wCs29oFa2Cdik9yyE
2QIDAQAB
-----END PUBLIC KEY-----

显然，两个公钥之间的格式有所不同。

OpenSSL 密钥始终以开头 “MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA”

我的钥匙以开头 "MIIBKwIBAAKCAQEA"

【问题讨论】：

公钥看起来总是不同的，因为它是基于一个新的和随机生成的p和q。

【参考方案1】：

不幸的是，您引用的答案中的代码并不正确 - 它导出 private 密钥 PEM 格式，但仅正确设置了公钥字段，这与导出不同标准格式的 RSA 公钥。

我实际上在other answer 中为该问题编写了代码，当时还编写了一种以标准格式导出公钥的模式，但由于不需要，因此未将其包含在该答案中。这里是：

private static void ExportPublicKey(RSACryptoServiceProvider csp, TextWriter outputStream)

    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);
            innerWriter.Write((byte)0x30); // SEQUENCE
            EncodeLength(innerWriter, 13);
            innerWriter.Write((byte)0x06); // OBJECT IDENTIFIER
            var rsaEncryptionOid = new byte[]  0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01 ;
            EncodeLength(innerWriter, rsaEncryptionOid.Length);
            innerWriter.Write(rsaEncryptionOid);
            innerWriter.Write((byte)0x05); // NULL
            EncodeLength(innerWriter, 0);
            innerWriter.Write((byte)0x03); // BIT STRING
            using (var bitStringStream = new MemoryStream())
            
                var bitStringWriter = new BinaryWriter(bitStringStream);
                bitStringWriter.Write((byte)0x00); // # of unused bits
                bitStringWriter.Write((byte)0x30); // SEQUENCE
                using (var paramsStream = new MemoryStream())
                
                    var paramsWriter = new BinaryWriter(paramsStream);
                    EncodeIntegerBigEndian(paramsWriter, parameters.Modulus); // Modulus
                    EncodeIntegerBigEndian(paramsWriter, parameters.Exponent); // Exponent
                    var paramsLength = (int)paramsStream.Length;
                    EncodeLength(bitStringWriter, paramsLength);
                    bitStringWriter.Write(paramsStream.GetBuffer(), 0, paramsLength);
                
                var bitStringLength = (int)bitStringStream.Length;
                EncodeLength(innerWriter, bitStringLength);
                innerWriter.Write(bitStringStream.GetBuffer(), 0, bitStringLength);
            
            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-----");
        for (var i = 0; i < base64.Length; i += 64)
        
            outputStream.WriteLine(base64, i, Math.Min(64, base64.Length - i));
        
        outputStream.WriteLine("-----END PUBLIC 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】：

您知道您的实现实际上是 Azure Powershell 中的 used 吗？

@foldone - 我现在做！谢谢你告诉我！

此解决方案完美运行。唯一的缺陷是我不能很好地理解流程，有没有解释或深入分析以更好地理解这个流程以及为什么会这样？