在我们使用RSA加密的时候，往往会需要公钥以及私钥，但是有时只有java的Base64的公钥和私钥；有需要的朋vb.net教程友可以c#教程参考下

C# 常用的加密算法，参考文章C#常用的加密算法EncryptionHelper类：MD5、Base64、SHA1、SHA256、HmacSHA256、DES、AES、RSA

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.X509;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using System.Xml;

namespace ConsoleApp3
{
    /// <summary>
    /// C# RAS生成.NET公钥与私钥以及.NET公钥与私钥转Java公钥私钥类
    /// </summary>
    public class RASKeyConversion
    {
        /// <summary>
        /// 第一个：C# 私钥；第二个：C# 公钥；第三个：JAVA私钥；第四个：JAVA公钥
        /// </summary>
        private static string[] sKeys = new String[4];

        /// <summary>
        /// 生成公钥与私钥方法
        /// </summary>
        /// <returns>第一个：C# 私钥；第二个：C# 公钥；第三个：JAVA私钥；第四个：JAVA公钥</returns>
        public static string[] createPulbicKey()
        {
            try
            {
                using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
                {
                    //C# 私钥
                    sKeys[0] = rsa.ToXmlString(true);
                    //C# 公钥
                    sKeys[1] = rsa.ToXmlString(false);
                    //JAVA私钥
                    sKeys[2] = RSAPrivateKeyDotNet2Java(sKeys[0]);
                    //JAVA公钥
                    sKeys[3] = RSAPublicKeyDotNet2Java(sKeys[1]);
                    return sKeys;
                }
            }
            catch (Exception)
            {
                return null;
            }
        }

        /// <summary>    
        /// RSA私钥格式转换，.net->java    
        /// </summary>    
        /// <param name="privateKey">.net生成的私钥</param>    
        /// <returns></returns>    
        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，.net->java    
        /// </summary>    
        /// <param name="publicKey">.net生成的公钥</param>    
        /// <returns></returns>    
        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);
        }
    }
}

本文来自博客园，作者：TomLucas