详细分析JAVA加解密算法

package other;

import java.security.MessageDigest;

/**
 * @author: rickiyang
 * @date: 2019/9/13
 * @description:
 */
public class MD5Test {

 static char[] hex = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

 public static void main(String[] args) {
 try {
  //申明使用MD5算法
  MessageDigest md5 = MessageDigest.getInstance("MD5");
  md5.update("a".getBytes());//
  System.out.println("md5(a)=" + byte2str(md5.digest()));
  md5.update("a".getBytes());
  md5.update("bc".getBytes());
  System.out.println("md5(abc)=" + byte2str(md5.digest()));
  //你会发现上面的md5值与下面的一样
  md5.update("abc".getBytes());
  System.out.println("md5(abc)=" + byte2str(md5.digest()));
 } catch (Exception e) {
  e.printStackTrace();
 }
 }

 /**
 * 将字节数组转换成十六进制字符串
 *
 * @param bytes
 * @return
 */
 private static String byte2str(byte[] bytes) {
 int len = bytes.length;
 StringBuffer result = new StringBuffer();
 for (int i = 0; i < len; i++) {
  byte byte0 = bytes[i];
  result.append(hex[byte0 >>> 4 & 0xf]);
  result.append(hex[byte0 & 0xf]);
 }
 return result.toString();
 }
}

//使用base64加密
BASE64Encoder encoder = new BASE64Encoder(); 
String encrypt = encoder.encode(str.getBytes()); 
//使用base64解密
BASE64Decoder decoder = new BASE64Decoder(); 
String decrypt = new String(decoder.decodeBuffer(encryptStr)); 

	/**
 * 创建密匙对
 *
 * @return
 */
 private KeyPair genKeyPair() {
 //创建 RSA Key 的生产者。
 KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");

 //利用用户密码作为随机数初始化出 1024 比特 Key 的生产者。
 //SecureRandom 是生成安全随机数序列，password.getBytes() 是种子，只要种子相同，序列就一样。
 keyPairGen.initialize(1024, new SecureRandom("password".getBytes()));

 //创建密钥对
 return keyPairGen.generateKeyPair();
 }


 /**
 * 生成公匙
 *
 * @return
 */
 public PublicKey genPublicKey() {
 try {
  //创建密钥对
  KeyPair keyPair = genKeyPair();

  //生成公钥
  PublicKey publicKey = keyPair.getPublic();
  X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKey.getEncoded());
  KeyFactory keyFactory = KeyFactory.getInstance("RSA");
  publicKey = keyFactory.generatePublic(keySpec);
  return publicKey;
 } catch (Exception e) {
  e.printStackTrace();
 }
 return null;

 }

 /**
 * 生成私匙
 *
 * @return
 */
 public PrivateKey genPrivateKey() {
 try {
  //创建密钥对
  KeyPair keyPair = genKeyPair();

  //生成私匙
  PrivateKey privateKey = keyPair.getPrivate();
  X509EncodedKeySpec keySpec = new X509EncodedKeySpec(privateKey.getEncoded());
  KeyFactory keyFactory = KeyFactory.getInstance("RSA");
  return keyFactory.generatePrivate(keySpec);
 } catch (Exception e) {
  e.printStackTrace();
 }
 return null;
 }

 /**
 * 公钥加密
 *
 * @param data
 * @param publicKey
 * @return
 * @throws Exception
 */
 public static byte[] encryptByPublicKey(byte[] data, String publicKey)
  throws Exception {
 X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(publicKey.getBytes());
 KeyFactory keyFactory = KeyFactory.getInstance("RSA");
 Key publicK = keyFactory.generatePublic(x509KeySpec);
 // 对数据加密
 Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
 cipher.init(Cipher.ENCRYPT_MODE, publicK);
 int inputLen = data.length;
 ByteArrayOutputStream out = new ByteArrayOutputStream();
 int offSet = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段加密
 while (inputLen - offSet > 0) {
  if (inputLen - offSet > 117) {
  cache = cipher.doFinal(data, offSet, 117);
  } else {
  cache = cipher.doFinal(data, offSet, inputLen - offSet);
  }
  out.write(cache, 0, cache.length);
  i++;
  offSet = i * 117;
 }
 byte[] encryptedData = out.toByteArray();
 out.close();
 return encryptedData;
 }

 /**
 * 私钥解密
 *
 * @param encryptedData
 * @param privateKey
 * @return
 * @throws Exception
 */
 public static byte[] decryptByPrivateKey(byte[] encryptedData,
      String privateKey) throws Exception {
 PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(privateKey.getBytes());
 KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
 Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
 Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
 cipher.init(Cipher.DECRYPT_MODE, privateK);
 int inputLen = encryptedData.length;
 ByteArrayOutputStream out = new ByteArrayOutputStream();
 int offSet = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段解密
 while (inputLen - offSet > 0) {
  if (inputLen - offSet > 118) {
  cache = cipher.doFinal(encryptedData, offSet, 118);
  } else {
  cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
  }
  out.write(cache, 0, cache.length);
  i++;
  offSet = i * 118;
 }
 byte[] decryptedData = out.toByteArray();
 out.close();
 return decryptedData;
 }

 /**
 * 私钥加密
 *
 * @param data
 * @param privateKey
 * @return
 * @throws Exception
 */
 public static byte[] encryptByPrivateKey(byte[] data, String privateKey)
  throws Exception {
 PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(publicKey.getBytes());
 KeyFactory keyFactory = KeyFactory.getInstance("RSA");
 Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
 Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
 cipher.init(Cipher.ENCRYPT_MODE, privateK);
 int inputLen = data.length;
 ByteArrayOutputStream out = new ByteArrayOutputStream();
 int offSet = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段加密
 while (inputLen - offSet > 0) {
  if (inputLen - offSet > 117) {
  cache = cipher.doFinal(data, offSet, 117);
  } else {
  cache = cipher.doFinal(data, offSet, inputLen - offSet);
  }
  out.write(cache, 0, cache.length);
  i++;
  offSet = i * 117;
 }
 byte[] encryptedData = out.toByteArray();
 out.close();
 return encryptedData;
 }

	/**
 * 公钥解密
 *
 * @param encryptedData
 * @param publicKey
 * @return
 * @throws Exception
 */
 public static byte[] decryptByPublicKey(byte[] encryptedData,
      String publicKey) throws Exception {
 X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(publicKey.getBytes());
 KeyFactory keyFactory = KeyFactory.getInstance("RSA");
 Key publicK = keyFactory.generatePublic(x509KeySpec);
 Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
 cipher.init(Cipher.DECRYPT_MODE, publicK);
 int inputLen = encryptedData.length;
 ByteArrayOutputStream out = new ByteArrayOutputStream();
 int offSet = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段解密
 while (inputLen - offSet > 0) {
  if (inputLen - offSet > 118) {
  cache = cipher.doFinal(encryptedData, offSet, 118);
  } else {
  cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
  }
  out.write(cache, 0, cache.length);
  i++;
  offSet = i * 118;
 }
 byte[] decryptedData = out.toByteArray();
 out.close();
 return decryptedData;
 }

public static void jdkHmacMD5() {
 try {
 // 初始化KeyGenerator
 KeyGenerator keyGenerator = KeyGenerator.getInstance("HmacMD5");
 // 产生密钥
 SecretKey secretKey = keyGenerator.generateKey();
 // 获取密钥
 byte[] key = secretKey.getEncoded();
 //  byte[] key = Hex.decodeHex(new char[]{'1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e'});
 // 还原密钥
 SecretKey restoreSecretKey = new SecretKeySpec(key, "HmacMD5");
 // 实例化MAC
 Mac mac = Mac.getInstance(restoreSecretKey.getAlgorithm());
 // 初始化MAC
 mac.init(restoreSecretKey);
 // 执行摘要
 byte[] hmacMD5Bytes = mac.doFinal("data".getBytes());
 System.out.println("jdk hmacMD5:" + new String(hmacMD5Bytes));
 } catch (Exception e) {
 e.printStackTrace();
 }
}