C# RSA 非对称加密

代码：

RSAHelper.cs(RSA加密工具类)：

using System;
using System.Security.Cryptography;
using System.Text;

namespace Utils
{
    /// <summary>
    /// RSA加密工具类
    /// </summary>
    public class RSAHelper
    {
        /// <summary>
        /// RSA加密
        /// </summary>
        public static string RSAEncrypt_LongContent(string publicKey, string content)
        {
            byte[] bytes = Encoding.UTF8.GetBytes(content);


            int pageSize = 117;
            int pageCount = (bytes.Length - 1) / pageSize + 1;

            StringBuilder result = new StringBuilder();
            for (int page = 1; page <= pageCount; page++)
            {
                int start = pageSize * (page - 1);

                byte[] subBytes = page == pageCount ? new byte[bytes.Length - start] : new byte[pageSize];

                Array.Copy(bytes, start, subBytes, 0, subBytes.Length);

                string strEncrypted = RSAEncrypt(publicKey, Encoding.UTF8.GetString(subBytes));
                result.Append(strEncrypted);
            }

            return result.ToString();
        }

        /// <summary>
        /// RSA解密
        /// </summary>
        public static string RSADecrypt_LongContent(string privateKey, string content)
        {
            int pageSize = 172;
            int pageCount = (content.Length - 1) / pageSize + 1;

            StringBuilder result = new StringBuilder();
            for (int page = 1; page <= pageCount; page++)
            {
                int start = pageSize * (page - 1);

                string subContent = null;
                if (page != pageCount)
                {
                    subContent = content.Substring(start, pageSize);
                }
                else
                {
                    subContent = content.Substring(start, content.Length - start);
                }

                string strEncrypted = RSADecrypt(privateKey, subContent);
                result.Append(strEncrypted);
            }

            return result.ToString();
        }

        /// <summary>
        /// RSA加密
        /// </summary>
        public static string RSAEncrypt(string publicKey, string content)
        {
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(publicKey);
            byte[] cipherBytes = rsa.Encrypt(Encoding.UTF8.GetBytes(content), false);

            return Convert.ToBase64String(cipherBytes);
        }

        /// <summary>
        /// RSA解密
        /// </summary>
        public static string RSADecrypt(string privateKey, string content)
        {
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(privateKey);
            byte[] cipherBytes = rsa.Decrypt(Convert.FromBase64String(content), false);

            return Encoding.UTF8.GetString(cipherBytes);
        }

        /// <summary>
        /// 创建公钥私钥
        /// </summary>
        public static RSAKey CreateKey()
        {
            RSAKey rsaKey = new RSAKey();

            using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
            {
                rsaKey.PublicKey_NET = rsa.ToXmlString(false); // 公钥
                rsaKey.PrivateKey_NET = rsa.ToXmlString(true); // 私钥

                rsaKey.PublicKey_Java = RSAKeyConvert.RSAPublicKeyDotNet2Java(rsaKey.PublicKey_NET);
                rsaKey.PrivateKey_Java = RSAKeyConvert.RSAPrivateKeyDotNet2Java(rsaKey.PrivateKey_NET);
            }

            return rsaKey;
        }
    }

    public class RSAKey
    {
        public string PublicKey_NET { get; set; }

        public string PrivateKey_NET { get; set; }

        public string PublicKey_Java { get; set; }

        public string PrivateKey_Java { get; set; }
    }
}

RSAKeyConvert.cs(Java .NET RSA密钥格式转换)(需要安装NuGet包BouncyCastle)：

using System;
using System.Xml;
using Org.BouncyCastle.Asn1.Pkcs;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Pkcs;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.X509;

namespace Utils
{
    /// <summary>   
    /// RSA密钥格式转换   
    /// </summary>   
    public class RSAKeyConvert
    {
        /// <summary>   
        /// RSA私钥格式转换，java->.net   
        /// </summary>   
        /// <param name="privateKey">java生成的RSA私钥</param>   
        public static string RSAPrivateKeyJava2DotNet(string privateKey)
        {
            RsaPrivateCrtKeyParameters privateKeyParam = (RsaPrivateCrtKeyParameters)PrivateKeyFactory.CreateKey(Convert.FromBase64String(privateKey));

            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(privateKeyParam.Modulus.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.PublicExponent.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.P.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.Q.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.DP.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.DQ.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.QInv.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.Exponent.ToByteArrayUnsigned()));
        }

        /// <summary>   
        /// RSA私钥格式转换，.net->java   
        /// </summary>   
        /// <param name="privateKey">.net生成的私钥</param>   
        public static string RSAPrivateKeyDotNet2Java(string privateKey)
        {
            XmlDocument doc = new XmlDocument();
            doc.LoadXml(privateKey);
            BigInteger m = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("Modulus")[0].InnerText));
            BigInteger exp = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("Exponent")[0].InnerText));
            BigInteger d = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("D")[0].InnerText));
            BigInteger p = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("P")[0].InnerText));
            BigInteger q = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("Q")[0].InnerText));
            BigInteger dp = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("DP")[0].InnerText));
            BigInteger dq = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("DQ")[0].InnerText));
            BigInteger qinv = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("InverseQ")[0].InnerText));

            RsaPrivateCrtKeyParameters privateKeyParam = new RsaPrivateCrtKeyParameters(m, exp, d, p, q, dp, dq, qinv);

            PrivateKeyInfo privateKeyInfo = PrivateKeyInfoFactory.CreatePrivateKeyInfo(privateKeyParam);
            byte[] serializedPrivateBytes = privateKeyInfo.ToAsn1Object().GetEncoded();
            return Convert.ToBase64String(serializedPrivateBytes);
        }

        /// <summary>   
        /// RSA公钥格式转换，java->.net   
        /// </summary>   
        /// <param name="publicKey">java生成的公钥</param>   
        public static string RSAPublicKeyJava2DotNet(string publicKey)
        {
            RsaKeyParameters publicKeyParam = (RsaKeyParameters)PublicKeyFactory.CreateKey(Convert.FromBase64String(publicKey));
            return string.Format("<RSAKeyValue><Modulus>{0}</Modulus><Exponent>{1}</Exponent></RSAKeyValue>",
                Convert.ToBase64String(publicKeyParam.Modulus.ToByteArrayUnsigned()),
                Convert.ToBase64String(publicKeyParam.Exponent.ToByteArrayUnsigned()));
        }

        /// <summary>   
        /// RSA公钥格式转换，.net->java   
        /// </summary>   
        /// <param name="publicKey">.net生成的公钥</param>    
        public static string RSAPublicKeyDotNet2Java(string publicKey)
        {
            XmlDocument doc = new XmlDocument();
            doc.LoadXml(publicKey);
            BigInteger m = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("Modulus")[0].InnerText));
            BigInteger p = new BigInteger(1, Convert.FromBase64String(doc.DocumentElement.GetElementsByTagName("Exponent")[0].InnerText));
            RsaKeyParameters pub = new RsaKeyParameters(false, m, p);

            SubjectPublicKeyInfo publicKeyInfo = SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(pub);
            byte[] serializedPublicBytes = publicKeyInfo.ToAsn1Object().GetDerEncoded();
            return Convert.ToBase64String(serializedPublicBytes);
        }
    }
}