场景：Java实现RSA，将公钥和秘钥分别输出文件，公钥用于加密，私钥用于解密。
重点要关注解密时，不能直接传String，要用byte[]，所以需要加二者转换函数。
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 java.security.NoSuchAlgorithmException;import javax.crypto.Cipher;import javax.crypto.NoSuchPaddingException;public class RSAAsymmetricEncryption {/*** 公钥加密，私钥解密(非对称加密)* */public static void main(String[] args) throws Exception {//生成公钥文件和秘钥文件并保存generateKey();//导入公钥加密String express="13366668888";byte[] cipherText=publicEnrypy(express);String strCiphertext=byteToString(cipherText);//密文byte[]转化成stringSystem.out.println(strCiphertext);//导入私钥解密byte[] getcipherText=stringToByte(strCiphertext);//密文string转化成byte[]byte[] retExpress=privateEncode(getcipherText);System.out.println(new String(retExpress));}//生成公钥和秘钥public static void generateKey() throws Exception{KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA"); KeyPair keyPair = keyPairGenerator.generateKeyPair();// 生成钥匙对 Key publicKey = keyPair.getPublic();// 得到公钥 String puckeyFile="D:\\tmp\\rsa_pubkey.dat";saveKey(publicKey,puckeyFile);//保存公钥Key privateKey = keyPair.getPrivate();// 得到私钥 String prikeyFile="D:\\tmp\\rsa_prikey.dat";saveKey(privateKey,prikeyFile);//把私钥保存到硬盘上 }//保存公钥和秘钥private static void saveKey(Key rsaKey,String filename) throws Exception{ObjectOutputStream outputStream = new ObjectOutputStream( new FileOutputStream(new File(filename)));outputStream.writeObject(rsaKey);}//导出公钥和秘钥private static Key loadKey(String filename) throws Exception {ObjectInputStream inputStream = new ObjectInputStream( new FileInputStream(new File(filename)));Key rsaKey = (Key) inputStream.readObject();return rsaKey;}/*** 加密的方法,使用公钥进行加密* @throws Exception*/public static byte[] publicEnrypy(String express) throws Exception {Cipher cipher = Cipher.getInstance("RSA");String puckeyFile="D:\\tmp\\rsa_pubkey.dat";Key pubkey=loadKey(puckeyFile);cipher.init(Cipher.ENCRYPT_MODE, pubkey);// 设置为加密模式byte[] result = cipher.doFinal(express.getBytes());// 对数据进行加密 return result;//返回密文}/*** 解密的方法，使用私钥进行解密* @throws Exception*/public static byte[] privateEncode(byte[] cipherText) throws Exception {Cipher cipher = Cipher.getInstance("RSA"); String prikeyFile="D:\\tmp\\rsa_prikey.dat";Key prikey = loadKey(prikeyFile);// 从硬盘中读取私钥 cipher.init(Cipher.DECRYPT_MODE, prikey);//设置为解密模式，用私钥解密 byte[] result = cipher.doFinal(cipherText);//对加密后的数据进行解密return result ;//返回明文 }// 把byte[]元素之间添加空格，并转化成字符串返回， public static String byteToString(byte[] resouce){StringBuffer sb = new StringBuffer(); for (int i = 0; i < resouce.length; i++) { if (i == resouce.length-1) { sb.append(Byte.toString(resouce[i]));}else{ sb.append(Byte.toString(resouce[i]));sb.append(" "); } } return sb.toString(); } // 把字符串按照空格进行拆分成数组，然后转化成byte[],返回 public static byte[] stringToByte(String resouce){ String[] strArr = resouce.split(" ");int len = strArr.length;byte[] clone = new byte[len];for (int i = 0; i < len; i++) { clone[i] = Byte.parseByte(strArr[i]);} return clone; } }
