C# RSA 公钥输出不正确

时间：2023-02-03

本文介绍了C# RSA 公钥输出不正确的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着跟版网的小编来一起学习吧！

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 命令成功地做到了这一点(一些输出被缩短了):

I am currently trying to generate and send a public RSA key using C#. It should be a 2048 bit long key in PEM format. I have successfully done so using OpenSSL command with the following (some output are shortened):

$ 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:

The following code is what I use to generate a public key using C#:

// 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://stackoverflow.com/a/25591659/2383179

The ExportPublicKeyToPEMFormat can be found from this thread: https://stackoverflow.com/a/25591659/2383179

我在 C# 中的输出如下所示:

使用 OpenSSL 的正确输出如下所示:

显然，两个公钥之间的格式有所不同.

Obviously there is something different with the formats between the two public key.

OpenSSL 密钥总是以开头MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA"

The OpenSSL key always starst with "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA"

我的密钥以开头MIIBKwIBAAKCAQEA"

My key starts with "MIIBKwIBAAKCAQEA"

推荐答案

不幸的是，您引用的答案中的代码并不真正正确 - 它导出一个私有密钥 PEM 格式，但只有公钥字段设置正确，这与以标准格式导出 RSA 公钥不同.

Unfortunately, the code in the answer you referenced isn't really correct - it exports a private key PEM format, but with only the public key fields correctly set, this is not the same as exporting an RSA public key in standard format.

我实际上在该问题的其他答案中编写了代码，并且当时编写了一种用于导出标准格式的公钥，但没有将其包含在该答案中，因为它不是必需的.这是:

I actually wrote the code in the other answer to that question, and at the time wrote a mode for exporting the public key in the standard format, but didn't include it in that answer as it wasn't required. Here it is:

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]);
        }
    }
}

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C# RSA 公钥输出不正确

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