JAVA加密算法-非对称加密算法（DH，RSA）的详细介绍

import javax.crypto.KeyAgreement;
import javax.crypto.interfaces.DHPrivateKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

//1 生成源密钥
//2 把源公钥交给目标，目标通过源公钥，生成目标公钥和私钥
//3 把目标公钥交给源
//4 双方使用对方的公钥和和自己的私钥，生成本地密钥
//5 如果双方生成本地密钥相同则完成密钥交换
public class DHUtil {

  public static final String PUBLIC_KEY = "DH_Public_Key";
  public static final String PRIVATE_KEY = "DH_Private_key";

  /**
   * 生成源密钥对
   * @return
   * @throws Exception
   */
  public static Map initSourceKey() throws Exception{
    //创建KeyPairGenerator的实例，选用DH算法
    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("DH");

    //初始化密钥长度，默认1024，可选范围512-65536 & 64的倍数
    keyPairGenerator.initialize(1024);

    //生成密钥对
    KeyPair keyPair = keyPairGenerator.generateKeyPair();
    DHPublicKey dhPublicKey = (DHPublicKey) keyPair.getPublic();
    DHPrivateKey dhPrivateKey = (DHPrivateKey) keyPair.getPrivate();

    //将密钥对放入Map
    Map keyMap = new HashMap();
    keyMap.put(PUBLIC_KEY, dhPublicKey);
    keyMap.put(PRIVATE_KEY, dhPrivateKey);
    return keyMap;
  }

  /**
   * 通过源公钥 生成 目标密钥对
   * @param sourcePublicKey
   * @return
   * @throws Exception
   */
  public static Map initTargetKey(byte[] sourcePublicKey) throws Exception {

    KeyFactory keyFactory = KeyFactory.getInstance("DH");

    //通过源公钥，生成keySpec，使用KeyFactory生成源PublicKey相关信息
    X509EncodedKeySpec keySpec = new X509EncodedKeySpec(sourcePublicKey);
    DHPublicKey sourcePublic = (DHPublicKey) keyFactory.generatePublic(keySpec);

    DHParameterSpec dhPublicKeyParams = sourcePublic.getParams();

    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("DH");
    keyPairGenerator.initialize(dhPublicKeyParams);

    KeyPair keyPair = keyPairGenerator.generateKeyPair();
    DHPublicKey dhPublicKey = (DHPublicKey) keyPair.getPublic();
    DHPrivateKey dhPrivateKey = (DHPrivateKey) keyPair.getPrivate();

    //将密钥对放入Map
    Map keyMap = new HashMap();
    keyMap.put(PUBLIC_KEY, dhPublicKey);
    keyMap.put(PRIVATE_KEY, dhPrivateKey);
    return keyMap;
  }

  /**
   * 使用一方的公钥和另一方的私钥，生成本地密钥
   * @return
   */
  public static byte[] generateLocalSecretKey(byte[] aPublicKey, byte[] bPrivateKey) throws Exception{
    KeyFactory keyFactory = KeyFactory.getInstance("DH");

    //通过A公钥，生成keySpec，使用KeyFactory生成A PublicKey相关信息
    X509EncodedKeySpec keySpec = new X509EncodedKeySpec(aPublicKey);
    PublicKey publicKey = keyFactory.generatePublic(keySpec);

    //通过B私钥，生成B PrivateKey相关信息
    PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(bPrivateKey);
    PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);

    //通过KeyAgreement对A的PublicKey和B的PrivateKey进行加密
    KeyAgreement keyAgreement = KeyAgreement.getInstance("DH");
    keyAgreement.init(privateKey);
    keyAgreement.doPhase(publicKey,true);


    return keyAgreement.generateSecret("AES").getEncoded();//算法使用对称加密算法（DES，DESede，AES）
    //return keyAgreement.generateSecret();        // 也可以不选择算法，使用默认方法计算
  }

  //获取公钥字节数组
  public static byte[] getPublicKey(Map map){
    return ((DHPublicKey) map.get(PUBLIC_KEY)).getEncoded();
  }

  //获取私钥字节数组
  public static byte[] getPrivateKey(Map map){
    return ((DHPrivateKey) map.get(PRIVATE_KEY)).getEncoded();
  }

  public static void main(String[] args) throws Exception {

    byte[] source_public_key;
    byte[] source_private_key;
    byte[] source_local_key;

    byte[] target_public_key;
    byte[] target_private_key;
    byte[] target_local_key;

    Map sourceKey = initSourceKey();
    source_public_key = getPublicKey(sourceKey);
    source_private_key = getPrivateKey(sourceKey);

    System.out.println("源公钥："+BytesToHex.fromBytesToHex(source_public_key));
    System.out.println("源私钥："+BytesToHex.fromBytesToHex(source_private_key));

    Map targetKey = initTargetKey(getPublicKey(sourceKey));
    target_public_key = getPublicKey(targetKey);
    target_private_key = getPrivateKey(targetKey);

    System.out.println("目标公钥："+BytesToHex.fromBytesToHex(target_public_key));
    System.out.println("目标私钥："+BytesToHex.fromBytesToHex(target_private_key));

    source_local_key = generateLocalSecretKey(target_public_key, source_private_key);
    target_local_key = generateLocalSecretKey(source_public_key, target_private_key);

    System.out.println("源本地密钥："+BytesToHex.fromBytesToHex(source_local_key));
    System.out.println("目标本地密钥："+BytesToHex.fromBytesToHex(target_local_key));
  }
}

import javax.crypto.Cipher;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.util.HashMap;
import java.util.Map;

/**
 * RSA加密工具
 */
public class RSAUtil {

  public static final String PUBLIC_KEY = "RSA_Public_Key";
  public static final String PRIVATE_KEY = "RSA_Private_Key";

  /**
   * 初始化密钥
   * @return
   * @throws Exception
   */
  public static Map initKey() throws Exception{
    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
    keyPairGenerator.initialize(1024);//512-65536 & 64的倍数
    KeyPair keyPair = keyPairGenerator.generateKeyPair();
    RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
    RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

    Map keyMap = new HashMap();
    keyMap.put(PUBLIC_KEY, publicKey);
    keyMap.put(PRIVATE_KEY, privateKey);
    return keyMap;
  }

  public static RSAPublicKey getPublicKey(Map keyMap) {
    return (RSAPublicKey) keyMap.get(PUBLIC_KEY);
  }

  public static RSAPrivateKey getPrivateKey(Map keyMap){
    return (RSAPrivateKey) keyMap.get(PRIVATE_KEY);
  }

  /**
   * 使用公钥对数据进行加密
   * @param data
   * @param publicKey
   * @return
   * @throws Exception
   */
  public static byte[] encrypt(byte[] data, RSAPublicKey publicKey) throws Exception{
    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.ENCRYPT_MODE,publicKey);
    return cipher.doFinal(data);
  }

  /**
   * 使用私钥解密
   * @param data
   * @param privateKey
   * @return
   * @throws Exception
   */
  public static byte[] decrypt(byte[] data, RSAPrivateKey privateKey) throws Exception{
    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.DECRYPT_MODE,privateKey);
    return cipher.doFinal(data);
  }

  public static void main(String[] args) throws Exception {
    String data = "周杰伦-东风破";
    Map keyMap = initKey();

    byte[] miwen = encrypt(data.getBytes(),getPublicKey(keyMap));
    System.out.println("加密后的内容："+BytesToHex.fromBytesToHex(miwen));

    byte[] plain = decrypt(miwen, getPrivateKey(keyMap));
    System.out.println("解密后的内容："+new String(plain));

  }
}