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【Java】 RSA算法 Android JAVA C#互通
作者:首君 / 发布于2015/11/4/ 1134
RSA算法属非对称加密算法，在实际使用中，往往客户端使用公钥进行加密传递敏感数据，服务端server使用私钥进行解密，这样防止中间人从网络获取敏感数据的明文。

	Android端主要代码如下：

	package com.example.rsatest;

	import java.io.UnsupportedEncodingException;
	import java.math.BigInteger;
	import java.security.KeyFactory;
	import java.security.KeyPair;
	import java.security.KeyPairGenerator;
	import java.security.NoSuchAlgorithmException;
	import java.security.PrivateKey;
	import java.security.PublicKey;
	import java.security.Signature;
	import java.security.interfaces.RSAPrivateCrtKey;
	import java.security.interfaces.RSAPublicKey;
	import java.security.spec.RSAPrivateCrtKeySpec;
	import java.security.spec.RSAPublicKeySpec;
	import java.util.Date;

	import javax.crypto.Cipher;

	public class RsaHelper
	{
	 /**
	 * 生成RSA密钥对(默认密钥长度为1024)
	 *
	 * @return
	 */
	 public static KeyPair generateRSAKeyPair()
	 {
	 return generateRSAKeyPair(1024);
	 }

	 /**
	 * 生成RSA密钥对
	 *
	 * @param keyLength 密钥长度，范围：512～2048
	 * @return
	 */
	 public static KeyPair generateRSAKeyPair(int keyLength)
	 {
	 try
	 {
	 KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA/ECB/PKCS1Padding");
	 kpg.initialize(keyLength);
	 return kpg.genKeyPair();
	 }
	 catch (NoSuchAlgorithmException e)
	 {
	 return null;
	 }
	 }

	 /*
	 * java端公钥转换成C#公钥
	 */
	 public static String encodePublicKeyToXml(PublicKey key)
	 {
	 if (!RSAPublicKey.class.isInstance(key))
	 {
	 return null;
	 }
	 RSAPublicKey pubKey = (RSAPublicKey) key;
	 StringBuilder sb = new StringBuilder();

	 sb.append("<RSAKeyValue>");
	 sb.append("<Modulus>")
	 .append(Base64Helper.encode(pubKey.getModulus().toByteArray()))
	 .append("</Modulus>");
	 sb.append("<Exponent>")
	 .append(Base64Helper.encode(pubKey.getPublicExponent().toByteArray()))
	 .append("</Exponent>");
	 sb.append("</RSAKeyValue>");
	 return sb.toString();
	 }

	 /*
	 * C#端公钥转换成java公钥
	 */
	 public static PublicKey decodePublicKeyFromXml(String xml)
	 {
	 xml = xml.replaceAll("\r", "").replaceAll("\n", "");
	 BigInteger modulus =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml,
	 "<Modulus>", "</Modulus>")));
	 BigInteger publicExponent =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml,
	 "<Exponent>", "</Exponent>")));

	 RSAPublicKeySpec rsaPubKey = new RSAPublicKeySpec(modulus, publicExponent);

	 KeyFactory keyf;
	 try
	 {
	 keyf = KeyFactory.getInstance("RSA");
	 return keyf.generatePublic(rsaPubKey);
	 }
	 catch (Exception e)
	 {
	 return null;
	 }
	 }

	 /*
	 * C#端私钥转换成java私钥
	 */
	 public static PrivateKey decodePrivateKeyFromXml(String xml)
	 {
	 xml = xml.replaceAll("\r", "").replaceAll("\n", "");
	 BigInteger modulus =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml,
	 "<Modulus>", "</Modulus>")));
	 BigInteger publicExponent =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml,
	 "<Exponent>", "</Exponent>")));
	 BigInteger privateExponent =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml, "<D>",
	 "</D>")));
	 BigInteger primeP =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml, "<P>",
	 "</P>")));
	 BigInteger primeQ =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml, "<Q>",
	 "</Q>")));
	 BigInteger primeExponentP =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml,
	 "<DP>", "</DP>")));
	 BigInteger primeExponentQ =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml,
	 "<DQ>", "</DQ>")));
	 BigInteger crtCoefficient =
	 new BigInteger(1, Base64Helper.decode(StringUtils.getMiddleString(xml,
	 "<InverseQ>", "</InverseQ>")));

	 RSAPrivateCrtKeySpec rsaPriKey =
	 new RSAPrivateCrtKeySpec(modulus, publicExponent, privateExponent, primeP,
	 primeQ, primeExponentP, primeExponentQ, crtCoefficient);

	 KeyFactory keyf;
	 try
	 {
	 keyf = KeyFactory.getInstance("RSA");
	 return keyf.generatePrivate(rsaPriKey);
	 }
	 catch (Exception e)
	 {
	 return null;
	 }
	 }

	 /*
	 * java端私钥转换成C#私钥
	 */
	 public static String encodePrivateKeyToXml(PrivateKey key)
	 {
	 if (!RSAPrivateCrtKey.class.isInstance(key))
	 {
	 return null;
	 }
	 RSAPrivateCrtKey priKey = (RSAPrivateCrtKey) key;
	 StringBuilder sb = new StringBuilder();

	 sb.append("<RSAKeyValue>");
	 sb.append("<Modulus>")
	 .append(Base64Helper.encode(priKey.getModulus().toByteArray()))
	 .append("</Modulus>");
	 sb.append("<Exponent>")
	 .append(Base64Helper.encode(priKey.getPublicExponent().toByteArray()))
	 .append("</Exponent>");
	 sb.append("<P>").append(Base64Helper.encode(priKey.getPrimeP().toByteArray()))
	 .append("</P>");
	 sb.append("<Q>").append(Base64Helper.encode(priKey.getPrimeQ().toByteArray()))
	 .append("</Q>");
	 sb.append("<DP>")
	 .append(Base64Helper.encode(priKey.getPrimeExponentP().toByteArray()))
	 .append("</DP>");
	 sb.append("<DQ>")
	 .append(Base64Helper.encode(priKey.getPrimeExponentQ().toByteArray()))
	 .append("</DQ>");
	 sb.append("<InverseQ>")
	 .append(Base64Helper.encode(priKey.getCrtCoefficient().toByteArray()))
	 .append("</InverseQ>");
	 sb.append("<D>")
	 .append(Base64Helper.encode(priKey.getPrivateExponent().toByteArray()))
	 .append("</D>");
	 sb.append("</RSAKeyValue>");
	 return sb.toString();
	 }

	 // 用公钥加密
	 public static byte[] encryptData(byte[] data, PublicKey pubKey)
	 {
	 try
	 {
	 Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
	 cipher.init(Cipher.ENCRYPT_MODE, pubKey);
	 return cipher.doFinal(data);
	 }
	 catch (Exception e)
	 {
	 return null;
	 }
	 }

	 // 用私钥解密
	 public static byte[] decryptData(byte[] encryptedData, PrivateKey priKey)
	 {
	 try
	 {
	 Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
	 cipher.init(Cipher.DECRYPT_MODE, priKey);
	 return cipher.doFinal(encryptedData);
	 }
	 catch (Exception e)
	 {
	 return null;
	 }
	 }

	 /**
	 * 根据指定公钥进行明文加密
	 *
	 * @param plainText 要加密的明文数据
	 * @param pubKey 公钥
	 * @return
	 */
	 public static String encryptDataFromStr(String plainText, PublicKey pubKey)
	 {

	 try
	 {
	 byte[] dataByteArray = plainText.getBytes("UTF-8");
	 byte[] encryptedDataByteArray = RsaHelper.encryptData(dataByteArray, pubKey);
	 return Base64Helper.encode(encryptedDataByteArray);
	 }
	 catch (UnsupportedEncodingException e)
	 {
	 // TODO Auto-generated catch block
	 e.printStackTrace();
	 return "";
	 }
	 }

	 /**
	 * 根据指定私钥对数据进行签名(默认签名算法为"SHA1withRSA")
	 *
	 * @param data 要签名的数据
	 * @param priKey 私钥
	 * @return
	 */
	 public static byte[] signData(byte[] data, PrivateKey priKey)
	 {
	 return signData(data, priKey, "SHA1withRSA");
	 }

	 /**
	 * 根据指定私钥和算法对数据进行签名
	 *
	 * @param data 要签名的数据
	 * @param priKey 私钥
	 * @param algorithm 签名算法
	 * @return
	 */
	 public static byte[] signData(byte[] data, PrivateKey priKey, String algorithm)
	 {
	 try
	 {
	 Signature signature = Signature.getInstance(algorithm);
	 signature.initSign(priKey);
	 signature.update(data);
	 return signature.sign();
	 }
	 catch (Exception ex)
	 {
	 return null;
	 }
	 }

	 /**
	 * 用指定的公钥进行签名验证(默认签名算法为"SHA1withRSA")
	 *
	 * @param data 数据
	 * @param sign 签名结果
	 * @param pubKey 公钥
	 * @return
	 */
	 public static boolean verifySign(byte[] data, byte[] sign, PublicKey pubKey)
	 {
	 return verifySign(data, sign, pubKey, "SHA1withRSA");
	 }

	 /**
	 * @param data 数据
	 * @param sign 签名结果
	 * @param pubKey 公钥
	 * @param algorithm 签名算法
	 * @return
	 */
	 public static boolean verifySign(byte[] data, byte[] sign, PublicKey pubKey,
	 String algorithm)
	 {
	 try
	 {
	 Signature signature = Signature.getInstance(algorithm);
	 signature.initVerify(pubKey);
	 signature.update(data);
	 return signature.verify(sign);
	 }
	 catch (Exception ex)
	 {
	 return false;
	 }
	 }

	 public static void main(String[] args)
	 {
	 KeyPair kp = RsaHelper.generateRSAKeyPair();
	 PublicKey pubKey = kp.getPublic();
	 PrivateKey priKey = kp.getPrivate();

	 String pubKeyXml = RsaHelper.encodePublicKeyToXml(pubKey);
	 String priKeyXml = RsaHelper.encodePrivateKeyToXml(priKey);
	 System.out.println("====公钥====");
	 System.out.println(pubKeyXml);
	 System.out.println("====私钥====");
	 System.out.println(priKeyXml);

	 PublicKey pubKey2 = RsaHelper.decodePublicKeyFromXml(pubKeyXml);
	 PrivateKey priKey2 = RsaHelper.decodePrivateKeyFromXml(priKeyXml);

	 System.out.println("====公钥对比====");
	 System.out.println(pubKey.toString());
	 System.out.println("------");
	 System.out.println(pubKey2.toString());

	 System.out.println("====私钥对比====");
	 System.out.println(priKey.toString());
	 System.out.println("------");
	 System.out.println(priKey2.toString());

	 try
	 {
	 String pubKeyXml3 =
	 "<RSAKeyValue><Modulus>rHESyuI3ny4MLsqDBalW9ySaodCL0e6Bsrl01Q5G1qm2wjUoGULazZSNqZY+JQNjU92tW3Snk5RPIkv+wDj+uOT9LTUjQImltHnzqMvbt06GipVXDOyBLTa7G/zRIe/CrjyJ+XEYX2xIhpe5ayowl3HHUpZ71jRNioyxaVVZ8S0=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";
	 String priKeyXml3 =
	 "<RSAKeyValue><Modulus>rHESyuI3ny4MLsqDBalW9ySaodCL0e6Bsrl01Q5G1qm2wjUoGULazZSNqZY+JQNjU92tW3Snk5RPIkv+wDj+uOT9LTUjQImltHnzqMvbt06GipVXDOyBLTa7G/zRIe/CrjyJ+XEYX2xIhpe5ayowl3HHUpZ71jRNioyxaVVZ8S0=</Modulus><Exponent>AQAB</Exponent><P>5a7uM+IeY8QMVQl0q88ZTqWbB555l7+366cUIClTN8z2ZXzTnWFCNoQzUrG14FouJFYumFZD12Ni5MkJK6gqSw==</P><Q>wDMhwwO4kz82uSG+FlCBr06fYk2COTg0TofmSp/5OrVqgkBIe7FgpTpVGzGLk0mvOLcy6UZftq//W0Saow6nZw==</Q><DP>FbjDgliiMyE5YVlxlUYSyKNU1BWivj09caXte1UtL5vMubBiewHVtz4tdGamIr+kmX8lDPcrl1Uo5yY0HdLbnQ==</DP><DQ>kIjjJsgxkWnEOUyKqjU4kSDK8x3ehDEkBLpmEFBlGCU9R14YJAyr5RUM0zpbABQ1VK1P9+UYLUYE/hmFQIHQmQ==</DQ><InverseQ>pxQDThwSnUZ4EaNaCPl1ovYypdQUZaZ/Sld1+0n8FEjkmRcGP1R9VMuj1ViPZg3rvm2GeP8Xv1SJqJUVueWiGA==</InverseQ><D>DxBNoPWEAF7IZ6n/KhZx52MGMw6BuFQKdm9m+lml7Iik03BLUXGapYzNlzvtr9QM8D2UMEIPhX/WLdvPpEEWVzGnD7XpLXjGwfu1ZkJRcXPEZEZ2subh5ZBqOWCFWKv5WwgGYWuYDLHfrBlBgSFWR8cZuyqkmMsWl4CiadXqGA0=</D></RSAKeyValue>";

	 System.out.println((new Date()).toLocaleString() + ": 加载公钥中。。。");
	 PublicKey pubKey3 = RsaHelper.decodePublicKeyFromXml(pubKeyXml3);
	 System.out.println((new Date()).toLocaleString() + ": 加载私钥中。。。");
	 PrivateKey priKey3 = RsaHelper.decodePrivateKeyFromXml(priKeyXml3);

	 String dataStr = "Java与.NET和平共处万岁！";
	 byte[] dataByteArray = dataStr.getBytes("utf-8");
	 System.out.println("data的Base64表示：" + Base64Helper.encode(dataByteArray));

	 System.out.println((new Date()).toLocaleString() + ": 加密中。。。"); // 加密
	 byte[] encryptedDataByteArray = RsaHelper.encryptData(dataByteArray, pubKey3);

	 System.out.println("encryptedData的Base64表示："
	 + Base64Helper.encode(encryptedDataByteArray));
	 System.out.println((new Date()).toLocaleString() + ": 解密中。。。"); // 解密
	 // byte[]
	 byte[] decryptedDataByteArray =
	 RsaHelper.decryptData(encryptedDataByteArray, priKey3);
	 System.out.println(new String(decryptedDataByteArray, "utf-8"));// 签名
	 System.out.println((new Date()).toLocaleString() + ": 签名中。。。");
	 byte[] signDataByteArray = RsaHelper.signData(dataByteArray, priKey3);
	 System.out.println("signData的Base64表示："
	 + Base64Helper.encode(signDataByteArray)); // 验签
	 System.out.println((new Date()).toLocaleString() + ": 验签中。。。");
	 boolean isMatch =
	 RsaHelper.verifySign(dataByteArray, signDataByteArray, pubKey3);
	 System.out.println("验签结果：" + isMatch);

	 }
	 catch (Exception ex)
	 {
	 ex.printStackTrace();
	 }
	 }
	}

	RsaHelper

	Android客户端调用示例：

	protected void onCreate(Bundle savedInstanceState)
	 {
	 super.onCreate(savedInstanceState);
	 setContentView(R.layout.activity_main);

	 btnencode = (Button) findViewById(R.id.btnencode);
	 btndecode = (Button) findViewById(R.id.btndecode);
	 txtinit = (EditText) findViewById(R.id.txtinit);
	 txtencoded = (EditText) findViewById(R.id.txtencoded);
	 txtencoded2 = (EditText) findViewById(R.id.txtencoded2);
	 lbldecoded = (TextView) findViewById(R.id.lbldecoded);

	 btnencode.setOnClickListener(new OnClickListener()
	 {

	 @Override
	 public void onClick(View v)
	 {
	 // TODO Auto-generated method stub

	 try
	 {
	 String strinit = txtinit.getText().toString().trim();
	 String rs = RsaHelper.encryptDataFromStr(strinit, publicKey);
	 txtencoded.setText(rs);
	 Log.e("decoded", rs);//将rs值拿到c#服务器可解密成功
	 }
	 catch (Exception e)
	 {
	 e.printStackTrace();
	 }

	 }
	 });

	 btndecode.setOnClickListener(new OnClickListener()
	 {

	 @Override
	 public void onClick(View v)
	 {

	 try
	 {
	 String strtxtencoded = txtencoded2.getText().toString().trim();
	
	 //C#端加密的内容 也可解密
	 //strtxtencoded = "E7lS+MJCDImpS664YmwbFA+OqYlrLzPOw4/Lkg5aUnjZ/ztQkuh+6LtLGLU5T4aLpErVgI1+1tj74fnz1vv4XApK797uvxAiVIY2izZfwIF4M993Bx7Yy7JfciobXowp+eKsxhp4yrLuOZbM1kdNyhfvvOlMZNiLaXLpKyZat6A=";
	
	 String rs = new String(RsaHelper.decryptData(
	 Base64Helper.decode(strtxtencoded), privateKey), "UTF-8");
	 lbldecoded.setText(rs);
	 Log.e("encoded", rs);
	 }
	 catch (Exception e)
	 {
	 e.printStackTrace();
	 }

	 }
	 });

	 }

	

	JAVA 客户端程序 加密示例：

	public class RSAClient {

	 private static int MAXENCRYPTSIZE = 117;
	 private static int MAXDECRYPTSIZE = 128;
	
	 public static void main(String[] args) {
	 /*
	 *
	 * 以下xml格式由c#服务端生成的公钥
	 <RSAKeyValue>
	 <Modulus>w9u2HfdbNZrmAUmXPbNmrhfy861qX4mzcCn69Ksl03Nz+Fq9gINZeN/vrfcWBzMyYxb2/J2TnGtpCLc0ls6gOTKDPbnQHwHr3oCzfvxNwvT2uoKQUBl4xMFw0TmvufMbheq6q3FCXUkVkAUC1cbQ/S9DqNp/veYcAavRDXtFdD0=</Modulus>
	 <Exponent>AQAB</Exponent>
	 </RSAKeyValue>
	 */
	 String modulus = "w9u2HfdbNZrmAUmXPbNmrhfy861qX4mzcCn69Ksl03Nz+Fq9gINZeN/vrfcWBzMyYxb2/J2TnGtpCLc0ls6gOTKDPbnQHwHr3oCzfvxNwvT2uoKQUBl4xMFw0TmvufMbheq6q3FCXUkVkAUC1cbQ/S9DqNp/veYcAavRDXtFdD0=";
	 String exponent ="AQAB";
	
	 PublicKey p =getPublicKey(modulus,exponent);

	 //使用上述公钥 针对明文123abc进行加密
	 //step1.将明文转为BASE64格式
	 try {
	 String password = encodeBase64("123abc".getBytes());
	 byte[] by = decodeBase64(password);
	 String mask = encrypt(by,p);
	 System.out.println("请将以下密文复制到c#端进行解密");
	 System.out.println(mask);
	 } catch (Exception e) {
	 // TODO Auto-generated catch block
	 e.printStackTrace();
	 }
	
	 }
	 public static String encodeBase64(byte[] input) throws Exception {
	 Class clazz = Class
	 .forName("com.sun.org.apache.xerces.internal.impl.dv.util.Base64");
	 Method mainMethod = clazz.getMethod("encode", byte[].class);
	 mainMethod.setAccessible(true);
	 Object retObj = mainMethod.invoke(null, new Object[] { input });
	 return (String) retObj;
	 }
	 public static byte[] decodeBase64(String input) throws Exception{
	 Class clazz=Class.forName("com.sun.org.apache.xerces.internal.impl.dv.util.Base64");
	 Method mainMethod= clazz.getMethod("decode", String.class);
	 mainMethod.setAccessible(true);
	 Object retObj=mainMethod.invoke(null, input);
	 return (byte[])retObj;
	 }
	
	 /**
	 * 返回RSA公钥
	 * @param modules
	 * @param exponent
	 * @return
	 */
	 public static PublicKey getPublicKey(String modulus, String exponent){
	 try {
	 byte[] m = decodeBase64(modulus);
	 byte[] e = decodeBase64(exponent);
	 BigInteger b1 = new BigInteger(1,m);
	 BigInteger b2 = new BigInteger(1,e);
	 KeyFactory keyFactory = KeyFactory.getInstance("RSA");
	 RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2);
	 return (RSAPublicKey) keyFactory.generatePublic(keySpec);
	 } catch (Exception e) {
	 e.printStackTrace();
	 return null;
	 }
	 }
	
	 public static String encrypt2(byte[] source, PublicKey publicKey) throws Exception {
	
	
	 }
	
	 public static String encrypt(byte[] source, PublicKey publicKey) throws Exception {
	 String encryptData ="";
	 try {
	 Cipher cipher = Cipher.getInstance("RSA");
	 cipher.init(Cipher.ENCRYPT_MODE, publicKey);
	 int length = source.length;
	 int offset = 0;
	 byte[] cache;
	 ByteArrayOutputStream outStream = new ByteArrayOutputStream();
	 int i = 0;
	 while(length - offset > 0){
	 if(length - offset > MAXENCRYPTSIZE){
	 cache = cipher.doFinal(source, offset, MAXENCRYPTSIZE);
	 }else{
	 cache = cipher.doFinal(source, offset, length - offset);
	 }
	 outStream.write(cache, 0, cache.length);
	 i++;
	 offset = i * MAXENCRYPTSIZE;
	 }
	 return encodeBase64(outStream.toByteArray());
	 } catch (NoSuchAlgorithmException e) {
	 e.printStackTrace();
	 } catch (NoSuchPaddingException e) {
	 e.printStackTrace();
	 } catch (InvalidKeyException e) {
	 e.printStackTrace();
	 } catch (IllegalBlockSizeException e) {
	 e.printStackTrace();
	 } catch (BadPaddingException e) {
	 e.printStackTrace();
	 }
	 return encryptData;
	 }
	 }

	JAVA Client

	

	服务器 端 C#代码：

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

	namespace RSA_Android_Demo
	{
	 /// <summary>
	 /// RSA 非对称加解密算法
	 /// </summary>
	 public class RSAHelper
	 {
	 private int MAXENCRYPTSIZE = 117;
	 private int MAXDECRYPTSIZE = 128;

	 public string priKeyXml
	 {
	 get;
	 private set;
	 }

	 public string pubKeyXml
	 {
	 get;
	 private set;
	 }

	
	 private RSAHelper(string privateKey, string publicKey)
	 {
	 this.priKeyXml = privateKey;
	 this.pubKeyXml = publicKey;
	 }

	 public static RSAHelper Load(string privateKey = "", string publicKey = "")
	 {
	 if (string.IsNullOrEmpty(privateKey) && string.IsNullOrEmpty(publicKey))
	 {
	 //无key时生成新密钥
	 return Instance;
	 }
	 return new RSAHelper(privateKey, publicKey);
	 }

	 /// <summary>
	 /// 随机生成公私钥并返回对象
	 /// </summary>
	 public static RSAHelper Instance
	 {
	 get
	 {
	 RSACryptoServiceProvider provider = new RSACryptoServiceProvider(1024);
	 var publicKeyXml = provider.ToXmlString(false);
	 //publickey:<RSAKeyValue><Modulus>w9u2HfdbNZrmAUmXPbNmrhfy861qX4mzcCn69Ksl03Nz+Fq9gINZeN/vrfcWBzMyYxb2/J2TnGtpCLc0ls6gOTKDPbnQHwHr3oCzfvxNwvT2uoKQUBl4xMFw0TmvufMbheq6q3FCXUkVkAUC1cbQ/S9DqNp/veYcAavRDXtFdD0=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>
	 var privateKeyXml = provider.ToXmlString(true);
	 //privatekey:<RSAKeyValue><Modulus>w9u2HfdbNZrmAUmXPbNmrhfy861qX4mzcCn69Ksl03Nz+Fq9gINZeN/vrfcWBzMyYxb2/J2TnGtpCLc0ls6gOTKDPbnQHwHr3oCzfvxNwvT2uoKQUBl4xMFw0TmvufMbheq6q3FCXUkVkAUC1cbQ/S9DqNp/veYcAavRDXtFdD0=</Modulus><Exponent>AQAB</Exponent><P>6tzaLZmY+hLLAifunWwcdUSfqTUvKOO5bJ8M1Zt34en40tfBaH9zml9gP8cmXaWyfpiZgHlPS9xlkLngudAiJw==</P><Q>1Xw2E1ufXsCM2JZahB6PH9pCgfD4XPjrqxF9xOWVvfbPmVBZByBIHYRs8ifbjIPvSKuaCfVFVStoIcOYrT9I+w==</Q><DP>mS4iPsuHMtM/BND2mEYC6ZkwaTP+5jRgo6+4tzkHH5lyaFHAG1/FDlJWfEJvi3SezmLI+zojtd6xf4s8PvS40Q==</DP><DQ>I91kMEhaM87hWpmXx05i+RTvy2iyMNxYqzqbCHMRfwJxye3npvzTYLIYo23ywl5/2pOJo1ajOTW7nsB/a8uP9Q==</DQ><InverseQ>EtYQvvBViXf7A5bgh+H4xLlBezD0yziBigoP/xcg1mcuI9Kb9rtPq64hQsajDYeNmm0Ibkxz9ihHr8+uWtdi5w==</InverseQ><D>HSivw2RZKvDlv1lSb/gumEqufALcbF7W3SMS3qxAVGvC3z27Ks/jWTCVwWOg3u+LV99KZC+dk1MWbxq/dJhMmBSiHOT6Sg7wvNMmX58zHl7Bhs702henzbr7CkiWrUcy3pVigr4olT9FlkjQkeEu9VfVW4TRGUDUkixTeh9MMC0=</D></RSAKeyValue>

	 return new RSAHelper(privateKeyXml, publicKeyXml);
	 }
	 }

	 /// <summary>
	 /// RSA公钥加密
	 /// </summary>
	 /// <param name="content"></param>
	 /// <param name="publicKeyXml">公钥xml串</param>
	 /// <returns></returns>
	 public string Encrypt(string content)
	 {
	 //string publickey = @"<RSAKeyValue><Modulus>w9u2HfdbNZrmAUmXPbNmrhfy861qX4mzcCn69Ksl03Nz+Fq9gINZeN/vrfcWBzMyYxb2/J2TnGtpCLc0ls6gOTKDPbnQHwHr3oCzfvxNwvT2uoKQUBl4xMFw0TmvufMbheq6q3FCXUkVkAUC1cbQ/S9DqNp/veYcAavRDXtFdD0=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";
	 RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
	 byte[] cipherbytes;
	 rsa.FromXmlString(pubKeyXml);
	 cipherbytes = rsa.Encrypt(Encoding.UTF8.GetBytes(content), false);

	 return Convert.ToBase64String(cipherbytes);
	 //return cipherbytes;
	 }
	 /// <summary>
	 /// RSA私钥解密
	 /// </summary>
	 /// <param name="encryptData">经过Base64编码的密文</param>
	 /// <param name="privateKeyXml">私钥xml串</param>
	 /// <returns>RSA解密后的数据</returns>
	 public string Decrypt(string encryptData)
	 {
	 string decryptData = "";
	 try
	 {
	 RSACryptoServiceProvider provider = new RSACryptoServiceProvider();
	 provider.FromXmlString(priKeyXml);
	 byte[] bEncrypt = Convert.FromBase64String(encryptData);
	 int length = bEncrypt.Length;
	 int offset = 0;
	 string cache;
	 int i = 0;
	 while (length - offset > 0)
	 {
	 if (length - offset > MAXDECRYPTSIZE)
	 {
	 cache = Encoding.UTF8.GetString(provider.Decrypt(GetSplit(bEncrypt, offset, MAXDECRYPTSIZE), false));
	 }
	 else
	 {
	 cache = Encoding.UTF8.GetString(provider.Decrypt(GetSplit(bEncrypt, offset, length - offset), false));
	 }
	 decryptData += cache;
	 i++;
	 offset = i * MAXDECRYPTSIZE;
	 }
	 }
	 catch (Exception e)
	 {
	 throw e;
	 }
	 return decryptData;
	 }

	 /// <summary>
	 /// 截取字节数组部分字节
	 /// </summary>
	 /// <param name="input"></param>
	 /// <param name="offset">起始偏移位</param>
	 /// <param name="length">截取长度</param>
	 /// <returns></returns>
	 private byte[] GetSplit(byte[] input, int offset, int length)
	 {
	 byte[] output = new byte[length];
	 for (int i = offset; i < offset + length; i++)
	 {
	 output[i - offset] = input[i];
	 }
	 return output;
	 }

	 }

	}

	RSAHelper

	

	C#调用示例

	public void TestDecry()
	 {
	 //java端的密文
	 //以下为android端加密后的密文
	 string pwd =
	 "VpEiGrV8BND+30z/5n03eS7UW/0ZF7NgVnCKPp/5IrpGRI/aoDb0iNehTez8Gcnl1C/g0q71UjLVMjywysbdoTBCaLBq/x85Fw31NNvzc5XOW4St01Q3+78JKkX1CCmSbOPpb2lvMb0D8iGiq3gLt3UZZpLLkbyBZDaXP2oHaIc=";
	 //Convert.ToBase64String(bytes);

	 //服务端私钥
	 string privateKey = "<RSAKeyValue><Modulus>w9u2HfdbNZrmAUmXPbNmrhfy861qX4mzcCn69Ksl03Nz+Fq9gINZeN/vrfcWBzMyYxb2/J2TnGtpCLc0ls6gOTKDPbnQHwHr3oCzfvxNwvT2uoKQUBl4xMFw0TmvufMbheq6q3FCXUkVkAUC1cbQ/S9DqNp/veYcAavRDXtFdD0=</Modulus><Exponent>AQAB</Exponent><P>6tzaLZmY+hLLAifunWwcdUSfqTUvKOO5bJ8M1Zt34en40tfBaH9zml9gP8cmXaWyfpiZgHlPS9xlkLngudAiJw==</P><Q>1Xw2E1ufXsCM2JZahB6PH9pCgfD4XPjrqxF9xOWVvfbPmVBZByBIHYRs8ifbjIPvSKuaCfVFVStoIcOYrT9I+w==</Q><DP>mS4iPsuHMtM/BND2mEYC6ZkwaTP+5jRgo6+4tzkHH5lyaFHAG1/FDlJWfEJvi3SezmLI+zojtd6xf4s8PvS40Q==</DP><DQ>I91kMEhaM87hWpmXx05i+RTvy2iyMNxYqzqbCHMRfwJxye3npvzTYLIYo23ywl5/2pOJo1ajOTW7nsB/a8uP9Q==</DQ><InverseQ>EtYQvvBViXf7A5bgh+H4xLlBezD0yziBigoP/xcg1mcuI9Kb9rtPq64hQsajDYeNmm0Ibkxz9ihHr8+uWtdi5w==</InverseQ><D>HSivw2RZKvDlv1lSb/gumEqufALcbF7W3SMS3qxAVGvC3z27Ks/jWTCVwWOg3u+LV99KZC+dk1MWbxq/dJhMmBSiHOT6Sg7wvNMmX58zHl7Bhs702henzbr7CkiWrUcy3pVigr4olT9FlkjQkeEu9VfVW4TRGUDUkixTeh9MMC0=</D></RSAKeyValue>";

	 //解密
	 string userpwd = RSAHelper.Load(privateKey: privateKey).Decrypt(pwd);

	

	 //C# 端用公钥加密
	 string publickey = @"<RSAKeyValue><Modulus>w9u2HfdbNZrmAUmXPbNmrhfy861qX4mzcCn69Ksl03Nz+Fq9gINZeN/vrfcWBzMyYxb2/J2TnGtpCLc0ls6gOTKDPbnQHwHr3oCzfvxNwvT2uoKQUBl4xMFw0TmvufMbheq6q3FCXUkVkAUC1cbQ/S9DqNp/veYcAavRDXtFdD0=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";

	 var abc = RSAHelper.Load(publicKey: publickey).Encrypt("abc123中文");//查将此生成的值拿到android工程中解密，至此达到RSA 的 C#&mdash;Android双方互通

	 //C#端也可 解密
	 string userpwd2 = RSAHelper.Load(privateKey: privateKey).Decrypt(abc);

	
	 }
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