1、RSA非对称加密算法

RSA加密算法是最常用的非对称加密算法，由罗纳德·李维斯特（Ron Rivest）、阿迪·萨莫尔（Adi Shamir）和伦纳德·阿德曼（Leonard Adleman）于1977年一起提出，RSA就是他们三人姓氏开头字母拼在一起组成的。非对称加密算法的特点就是加密秘钥和解密秘钥不同，秘钥分为公钥和私钥，用私钥加密的明文，只能用公钥解密；用公钥加密的明文，只能用私钥解密。

RSA是第一个比较完善的公开密钥算法，它既能用于加密，也能用于数字签名。这个算法经受住了多年深入的密码分析，虽然密码分析者既不能证明也不能否定RSA的安全性，但这恰恰说明该算法有一定的可信性，目前它已经成为最流行的公开密钥算法。RSA的安全基于大数分解的难度。其公钥和私钥是一对大素数（100到200位十进制数或更大）的函数。从一个公钥和密文恢复出明文的难度，等价于分解两个大素数之积。

2、通过扩展方法写入和读取xml配置文件参数

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Threading.Tasks;
using System.Xml;
namespace CJavaPy.Encrypt
{
    public static class RSACryptoServiceProviderExtensions
    {
        public static void FromXmlString(this RSACryptoServiceProvider rsa, string xmlString)
        {
            RSAParameters parameters = new RSAParameters();
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml(xmlString);
            if (xmlDoc.DocumentElement.Name.Equals("RSAKeyValue"))
            {
                foreach (XmlNode node in xmlDoc.DocumentElement.ChildNodes)
                {
                    switch (node.Name)
                    {
                        case "Modulus": parameters.Modulus = Convert.FromBase64String(node.InnerText); break;
                        case "Exponent": parameters.Exponent = Convert.FromBase64String(node.InnerText); break;
                        case "P": parameters.P = Convert.FromBase64String(node.InnerText); break;
                        case "Q": parameters.Q = Convert.FromBase64String(node.InnerText); break;
                        case "DP": parameters.DP = Convert.FromBase64String(node.InnerText); break;
                        case "DQ": parameters.DQ = Convert.FromBase64String(node.InnerText); break;
                        case "InverseQ": parameters.InverseQ = Convert.FromBase64String(node.InnerText); break;
                        case "D": parameters.D = Convert.FromBase64String(node.InnerText); break;
                    }
                }
            }
            else
            {
                throw new Exception("Invalid XML RSA key.");
            }
            rsa.ImportParameters(parameters);
        }
        public static string ToXmlString(this RSACryptoServiceProvider rsa, bool includePrivateParameters)
        {
            RSAParameters parameters = rsa.ExportParameters(includePrivateParameters);
            return string.Format("<RSAKeyValue><Modulus>{0}</Modulus><Exponent>{1}</Exponent><P>{2}</P><Q>{3}</Q><DP>{4}</DP><DQ>{5}</DQ><InverseQ>{6}</InverseQ><D>{7}</D></RSAKeyValue>",
                Convert.ToBase64String(parameters.Modulus),
                Convert.ToBase64String(parameters.Exponent),
                Convert.ToBase64String(parameters.P),
                Convert.ToBase64String(parameters.Q),
                Convert.ToBase64String(parameters.DP),
                Convert.ToBase64String(parameters.DQ),
                Convert.ToBase64String(parameters.InverseQ),
                Convert.ToBase64String(parameters.D));
        }
    }
}

3、实现公钥和私钥加解密工具类

using System;
using System.IO;
using System.Reflection;
using System.Security.Cryptography;
using Microsoft.AspNetCore.Hosting;
namespace CJavaPy.Encrypt
{
    public class EncryptService 
    {
        private const string Path = "Encrypt/";
        private const string PrivateKeyFile = "Private.config";
        private const string PublicKeyFile = "Public.config";
        private readonly string _folder;
        private readonly string _privateKeyFileName;
        private readonly string _publicKeyFileName;
        public EncryptService(IWebHostEnvironment hostingEnvironment)
        {
            _folder = System.IO.Path.Combine(hostingEnvironment.ContentRootPath, Path);
            _privateKeyFileName = System.IO.Path.Combine(_folder, PrivateKeyFile);
            _publicKeyFileName = System.IO.Path.Combine(_folder, PublicKeyFile);
        }
        public byte[] Encrypt(byte[] source)
        {
            Func<byte[], byte[]> encrypt = sou =>
            {
                using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
                {                    
                    if (!Directory.Exists(_folder))
                    {
                        Directory.CreateDirectory(_folder);
                    }
                    if (!File.Exists(_privateKeyFileName))
                    {
                        File.WriteAllText(_privateKeyFileName, rsa.ToXmlString(true));
                        File.WriteAllText(_publicKeyFileName, rsa.ToXmlString(false));
                    }
                    rsa.FromXmlString(File.ReadAllText(_publicKeyFileName));
                    int maxBlockSize = rsa.KeySize / 8 - 11;
                    if (sou.Length <= maxBlockSize)
                        return rsa.Encrypt(sou, false);
                    using (MemoryStream plaiStream = new MemoryStream(sou))
                    {
                        using (MemoryStream crypStream = new MemoryStream())
                        {
                            byte[] buffer = new byte[maxBlockSize];
                            int blockSize = plaiStream.Read(buffer, 0, maxBlockSize);
                            while (blockSize > 0)
                            {
                                byte[] toEncrypt = new byte[blockSize];
                                Array.Copy(buffer, 0, toEncrypt, 0, blockSize);
                                byte[] cryptograph = rsa.Encrypt(toEncrypt, false);
                                crypStream.Write(cryptograph, 0, cryptograph.Length);
                                blockSize = plaiStream.Read(buffer, 0, maxBlockSize);
                            }
                            return crypStream.ToArray();
                        }
                    }
                }
            };
            return MarkData(encrypt(source));
        }
        public byte[] Decrypt(byte[] source)
        {
            if (IsEncrypt(source))
            {
                Func<byte[], byte[]> decrypt = sou =>
                {
                    using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
                    {
                        if (File.Exists(_folder + PrivateKeyFile))
                        {
                            rsa.FromXmlString(File.ReadAllText(_privateKeyFileName));
                        }
                        int maxBlockSize = rsa.KeySize / 8;
                        if (sou.Length <= maxBlockSize)
                            return rsa.Decrypt(sou, false);
                        using (MemoryStream crypStream = new MemoryStream(sou))
                        {
                            using (MemoryStream plaiStream = new MemoryStream())
                            {
                                byte[] buffer = new byte[maxBlockSize];
                                int blockSize = crypStream.Read(buffer, 0, maxBlockSize);
                                while (blockSize > 0)
                                {
                                    byte[] toDecrypt = new byte[blockSize];
                                    Array.Copy(buffer, 0, toDecrypt, 0, blockSize);
                                    byte[] plaintext = rsa.Decrypt(toDecrypt, false);
                                    plaiStream.Write(plaintext, 0, plaintext.Length);
                                    blockSize = crypStream.Read(buffer, 0, maxBlockSize);
                                }
                                return plaiStream.ToArray();
                            }
                        }
                    }
                };
                return decrypt(ClearDataMark(source));
            }
            return source;
        }
        private byte[] MarkData(byte[] source)
        {
            byte[] newBytes = new byte[source.Length + 200];
            for (int i = 0; i < newBytes.Length; i++)
            {
                if (i < 100 || i > newBytes.Length - 100 - 1)
                {
                    newBytes[i] = 0;
                }
                else
                {
                    newBytes[i] = source[i - 100];
                }
            }
            return newBytes;
        }
        private byte[] ClearDataMark(byte[] source)
        {
            byte[] newBytes = new byte[source.Length - 200];
            for (int i = 100; i < source.Length - 100; i++)
            {
                newBytes[i - 100] = source[i];
            }
            return newBytes;
        }
        private bool IsEncrypt(byte[] source)
        {
            for (int i = 0; i < 100; i++)
            {
                if (source[i] != 0 || source[source.Length - i - 1] != 0)
                {
                    return false;
                }
            }
            return true;
        }
    }
}

4、使用方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using CJavaPy.Encrypt;
namespace  CJavaPy.Encrypt
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }
        public IConfiguration Configuration { get; }
        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddRazorPages();
        }
        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
                app.UseHsts();
            }
           //调用示例代码
           EncryptService encryptService = new EncryptService(env);
           //配置文件不存在会自动生成
            byte[] data= encryptService.Encrypt(System.Text.Encoding.UTF8.GetBytes("www.cjavapy.com"));
            string val = System.Text.Encoding.UTF8.GetString(encryptService.Decrypt(data));
            string valOrigin = System.Text.Encoding.UTF8.GetString(data);
            app.UseHttpsRedirection();
            app.UseStaticFiles();
            app.UseRouting();
            app.UseAuthorization();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapRazorPages();
            });
        }
    }
}