因為C#的RSA加密解密只有公鑰加密，私鑰解密，沒有私鑰加密，公鑰解密。在網上查了很久也沒有很好的實現。BouncyCastle的文檔少之又少。很多人可能會說，C#也是可以的，通過Biginteger開源類來實現，不過那個是有一個文章，不過他加密出來的是16進制結果的。根本不能和JAVA互通。連加密出來的都不和C#原生的加密出來的結果格式一樣。所以還是沒有好的解決方法。

接下來還是不斷的找資料，找方法。找朋友找同事。個個都找。問題是有的，方法也是有的，所以總結各路大神之後寫了這個類。實現了私鑰加密，公鑰解密。並通過在線的校驗之後，發布上來。大家可以做一個DEMO，然後進去在線RSA加密解密校驗。

在線RSA，DES等加密解密地址：

http://tool.chacuo.net/cryptrsapubkey

下面直接粘貼代碼，不多說：

BouncyCastle相關DLL，估計不用我多說，大家可以百度下載。然後引用就可以了！

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Org.BouncyCastle.Asn1.Pkcs;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Crypto.Generators;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Pkcs;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Crypto.Engines;
using Org.BouncyCastle.X509;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Crypto.Encodings;

namespace CryptionUtils
{
    public class RSAForJava
    {

        public RSAForJava()
        {
             
        }
        /// <summary>
        /// KEY 結構體
        /// </summary>
        public struct RSAKEY
        {
            /// <summary>
            /// 公鑰
            /// </summary>
            public string PublicKey
            {
                get;
                set;
            }
            /// <summary>
            /// 私鑰
            /// </summary>
            public string PrivateKey
            {
                get;
                set;
            }
        }
        public RSAKEY GetKey()
        {
            //RSA密鑰對的構造器  
            RsaKeyPairGenerator keyGenerator = new RsaKeyPairGenerator();

            //RSA密鑰構造器的參數  
            RsaKeyGenerationParameters param = new RsaKeyGenerationParameters(
                Org.BouncyCastle.Math.BigInteger.ValueOf(3),
                new Org.BouncyCastle.Security.SecureRandom(),
                1024,   //密鑰長度  
                25);
            //用參數初始化密鑰構造器  
            keyGenerator.Init(param);
            //產生密鑰對  
            AsymmetricCipherKeyPair keyPair = keyGenerator.GenerateKeyPair();
            //獲取公鑰和密鑰  
            AsymmetricKeyParameter publicKey = keyPair.Public;
            AsymmetricKeyParameter privateKey = keyPair.Private;

            SubjectPublicKeyInfo subjectPublicKeyInfo = SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(publicKey);
            PrivateKeyInfo privateKeyInfo = PrivateKeyInfoFactory.CreatePrivateKeyInfo(privateKey);

            
            Asn1Object asn1ObjectPublic = subjectPublicKeyInfo.ToAsn1Object();

            byte[] publicInfoByte = asn1ObjectPublic.GetEncoded("UTF-8");
            Asn1Object asn1ObjectPrivate = privateKeyInfo.ToAsn1Object();
            byte[] privateInfoByte = asn1ObjectPrivate.GetEncoded("UTF-8");  

            RSAKEY item = new RSAKEY()
            {
                PublicKey =Convert.ToBase64String(publicInfoByte),
                PrivateKey=Convert.ToBase64String(privateInfoByte)
            };
            return item;
        }
        private AsymmetricKeyParameter GetPublicKeyParameter(string s)
        {
            s = s.Replace("\r", "").Replace("\n", "").Replace(" ","");
            byte[] publicInfoByte = Convert.FromBase64String(s);
            Asn1Object pubKeyObj = Asn1Object.FromByteArray(publicInfoByte);//這裏也可以從流中讀取，從本地導入   
            AsymmetricKeyParameter pubKey = PublicKeyFactory.CreateKey(publicInfoByte);
            return pubKey;
        }
        private AsymmetricKeyParameter GetPrivateKeyParameter(string s)
        {
            s = s.Replace("\r", "").Replace("\n", "").Replace(" ", "");
            byte[] privateInfoByte = Convert.FromBase64String(s);
           // Asn1Object priKeyObj = Asn1Object.FromByteArray(privateInfoByte);//這裏也可以從流中讀取，從本地導入   
           // PrivateKeyInfo privateKeyInfo = PrivateKeyInfoFactory.CreatePrivateKeyInfo(privateKey);
            AsymmetricKeyParameter priKey = PrivateKeyFactory.CreateKey(privateInfoByte);
            return priKey;
        }
        public string EncryptByPrivateKey(string s,string key)
        {
            //非對稱加密算法，加解密用  
            IAsymmetricBlockCipher engine = new Pkcs1Encoding(new RsaEngine());
          
          
            //加密  
            
            try
            {
                engine.Init(true, GetPrivateKeyParameter(key));
                byte[] byteData = System.Text.Encoding.UTF8.GetBytes(s);
                var ResultData = engine.ProcessBlock(byteData, 0, byteData.Length);
                return Convert.ToBase64String(ResultData);
                //Console.WriteLine("密文（base64編碼）:" + Convert.ToBase64String(testData) + Environment.NewLine);
            }
            catch (Exception ex)
            {
                return ex.Message;
                
            }  
        }
        public string DecryptByPublicKey(string s,string key)
        {
            s = s.Replace("\r", "").Replace("\n", "").Replace(" ", "");
            //非對稱加密算法，加解密用  
            IAsymmetricBlockCipher engine = new Pkcs1Encoding( new RsaEngine());
              

            //解密  
            
            try
            {
                engine.Init(false, GetPublicKeyParameter(key));
                byte[] byteData = Convert.FromBase64String(s);
                var ResultData = engine.ProcessBlock(byteData, 0, byteData.Length);
                return System.Text.Encoding.UTF8.GetString(ResultData);
                
            }
            catch (Exception ex)
            {
                return ex.Message;
                 
            }  
        }
    }
}

C# 與JAVA 的RSA 加密解密交互，互通，C#使用BouncyCastle來實現私鑰加密，公鑰解密的方法