How to Easily Create Self-Signed Certificates in C# Without P/Invoke?

C# Self-Signed Certificate Creation Guide: Comprehensive Analysis

In various scenarios, especially local encryption, it is necessary to create self-signed certificates. Although it is possible to use Crypt32.dll's P/Invoke implementation, this method can be complex and tedious. This article explores a more direct, P/Invoke-free method using the System.Security.Cryptography.X509Certificates namespace.

In .NET 4.7.2 and later, the CertificateRequest class provides a simplified method of generating self-signed certificates.

Create a self-signed certificate

The following code snippet demonstrates the process of creating a self-signed certificate:

<code class="language-csharp">using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;

public class CertificateUtil
{
    public static void CreateSelfSignedCertificate()
    {
        // 生成非对称密钥对。
        ECDsa ecdsa = ECDsa.Create();

        // 创建证书请求。
        CertificateRequest request = new CertificateRequest("cn=foobar", ecdsa, HashAlgorithmName.SHA256);

        // 创建自签名证书。
        X509Certificate2 certificate = request.CreateSelfSigned(DateTimeOffset.Now, DateTimeOffset.Now.AddYears(5));

        // 将证书导出为包含私钥的PFX (PKCS #12) 格式。
        byte[] pfxBytes = certificate.Export(X509ContentType.Pfx, "P@55w0rd");
        File.WriteAllBytes("mycert.pfx", pfxBytes);

        // 将证书导出为Base64编码的CER格式（仅包含公钥）。
        string cerContents = "-----BEGIN CERTIFICATE-----\r\n" +
                              Convert.ToBase64String(certificate.Export(X509ContentType.Cert), Base64FormattingOptions.InsertLineBreaks) +
                              "\r\n-----END CERTIFICATE-----";
        File.WriteAllText("mycert.cer", cerContents);
    }
}</code>

This method uses Elliptic Curve Digital Signature Algorithm (ECDSA) and SHA-256 hashing to generate a self-signed certificate. The certificate is valid for five years and can be exported to PFX (PKCS #12) and CER formats.

Summary

The System.Security.Cryptography.X509Certificates namespace in .NET provides a straightforward mechanism for creating self-signed certificates in C#. This article outlines the process of generating, exporting, and storing certificates, providing a P/Invoke-free, cross-platform solution to your local encryption needs.

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