RSA适用场景：
1）乙方生成两把密钥（公钥和私钥）。公钥是公开的，任何人都可以获得，私钥则是保密的。
2）甲方获取乙方的公钥，然后用它对信息加密。
3）乙方得到加密后的信息，用私钥解密。
参考代码如下：
package sk.ml;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.security.Key;import java.security.KeyPair;import java.security.KeyPairGenerator;import javax.crypto.Cipher;public class RSAAsymmetricEncryption {/*** 公钥加密，私钥解密(非对称加密)* */public static void main(String[] args) throws Exception {//公钥加密String express="abc";publicEnrypy(express);//私钥解密privateEncode();}/*** 加密的方法,使用公钥进行加密* @throws Exception*/public static void publicEnrypy(String express) throws Exception {Cipher cipher = Cipher.getInstance("RSA");KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA"); KeyPair keyPair = keyPairGenerator.generateKeyPair();// 生成钥匙对 Key publicKey = keyPair.getPublic();// 得到公钥Key privateKey = keyPair.getPrivate();// 得到私钥 saveKey(privateKey);//把私钥保存到硬盘上 cipher.init(Cipher.ENCRYPT_MODE, publicKey);// 设置为加密模式byte[] result = cipher.doFinal(express.getBytes());// 对数据进行加密 saveData(result);//把加密后的数据保存到硬盘上System.out.println(result.toString());//显示密文}/*** 解密的方法，使用私钥进行解密* @throws Exception*/public static void privateEncode() throws Exception {Cipher cipher = Cipher.getInstance("RSA");Key privateKey = loadKey();// 从硬盘中读取私钥 cipher.init(Cipher.DECRYPT_MODE, privateKey);//设置为解密模式，用私钥解密 byte[] data = loadData();// 从硬盘中读取加密后的数据 byte[] result = cipher.doFinal(data);//对加密后的数据进行解密，返回解密后的结果System.out.println( new String(result) );//显示明文}/*** 从硬盘中加载加密后的文件* @return* @throws FileNotFoundException* @throws IOException*/private static byte[] loadData() throws FileNotFoundException, IOException {FileInputStream fileInputStream = new FileInputStream(new File("D:\\tmp\\rsa.dat"));ByteArrayOutputStream outputStream = new ByteArrayOutputStream();byte[] buffer = new byte[1024];int len = 0;while ((len = fileInputStream.read(buffer)) != -1) {outputStream.write(buffer, 0, len);}fileInputStream.close();return outputStream.toByteArray();}/*** 把加密后的密文保存到硬盘上* @param result* @throws FileNotFoundException* @throws IOException*/private static void saveData(byte[] result) throws FileNotFoundException, IOException {FileOutputStream fileOutputStream = new FileOutputStream(new File("D:\\tmp\\rsa.dat"));fileOutputStream.write(result);}/*** 从硬盘中加载私钥* @return* @throws IOException* @throws FileNotFoundException* @throws ClassNotFoundException*/private static Key loadKey() throws IOException, FileNotFoundException, ClassNotFoundException {ObjectInputStream inputStream = new ObjectInputStream( new FileInputStream(new File("D:\\tmp\\rsa_prikey.dat")));Key privateKey = (Key) inputStream.readObject();return privateKey;}/*** 把私钥保存到硬盘上* @param privateKey* @throws IOException* @throws FileNotFoundException*/private static void saveKey(Key privateKey) throws IOException, FileNotFoundException {ObjectOutputStream outputStream = new ObjectOutputStream( new FileOutputStream(new File("D:\\tmp\\rsa_prikey.dat")));outputStream.writeObject(privateKey);}}
