Java对称与非对称加密算法原理详细讲解

import java.security.*;
import java.util.Base64;
import javax.crypto.*;
import javax.crypto.spec.*;
public class Main {
    public static void main(String[] args) throws Exception {
        // 原文:
        String message = "Hello, world!";
        System.out.println("Message(原始信息): " + message);
        // 128位密钥 = 16 bytes Key:
        byte[] key = "1234567890abcdef".getBytes();
        // 加密:
        byte[] data = message.getBytes();
        byte[] encrypted = encrypt(key, data);
        System.out.println("Encrypted(加密内容): " + 
        					Base64.getEncoder().encodeToString(encrypted));
        // 解密:
        byte[] decrypted = decrypt(key, encrypted);
        System.out.println("Decrypted(解密内容): " + new String(decrypted));
    }
    // 加密:
    public static byte[] encrypt(byte[] key, byte[] input) throws GeneralSecurityException {
    	// 创建密码对象，需要传入算法/工作模式/填充模式
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        // 根据key的字节内容，"恢复"秘钥对象
        SecreTKEy keySpec = new SecretKeySpec(key, "AES");
        // 初始化秘钥:设置加密模式ENCRYPT_MODE
        cipher.init(Cipher.ENCRYPT_MODE, keySpec);
        // 根据原始内容(字节),进行加密
        return cipher.doFinal(input);
    }
    // 解密:
    public static byte[] decrypt(byte[] key, byte[] input) throws GeneralSecurityException {
    	// 创建密码对象，需要传入算法/工作模式/填充模式
    	Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
    	// 根据key的字节内容，"恢复"秘钥对象
        SecretKey keySpec = new SecretKeySpec(key, "AES");
        // 初始化秘钥:设置解密模式DECRYPT_MODE
        cipher.init(Cipher.DECRYPT_MODE, keySpec);
        // 根据原始内容(字节),进行解密
        return cipher.doFinal(input);
    }
}

package com.apesource.demo04;
import java.security.*;
import java.util.Base64;
import javax.crypto.*;
import javax.crypto.spec.*;
public class Main {
	public static void main(String[] args) throws Exception {
        // 原文:
        String message = "Hello, world!";
        System.out.println("Message(原始信息): " + message);
        // 256位密钥 = 32 bytes Key:
        byte[] key = "1234567890abcdef1234567890abcdef".getBytes();
        // 加密:
        byte[] data = message.getBytes();
        byte[] encrypted = encrypt(key, data);
        System.out.println("Encrypted(加密内容): " + 
				Base64.getEncoder().encodeToString(encrypted));
        // 解密:
        byte[] decrypted = decrypt(key, encrypted);
        System.out.println("Decrypted(解密内容): " + new String(decrypted));
    }
    // 加密:
    public static byte[] encrypt(byte[] key, byte[] input) throws GeneralSecurityException {
        // 设置算法/工作模式CBC/填充
    	Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    	// 恢复秘钥对象
        SecretKeySpec keySpec = new SecretKeySpec(key, "AES");
        // CBC模式需要生成一个16 bytes的initialization vector:
        SecureRandom sr = SecureRandom.getInstanceStrong();
        byte[] iv = sr.generateSeed(16); // 生成16个字节的随机数
        System.out.println(Arrays.toString(iv));
        IvParameterSpec ivps = new IvParameterSpec(iv); // 随机数封装成IvParameterSpec参数对象
        // 初始化秘钥:操作模式、秘钥、IV参数
        cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivps);
        // 加密
        byte[] data = cipher.doFinal(input);
        // IV不需要保密，把IV和密文一起返回:
        return join(iv, data);
    }
    // 解密:
    public static byte[] decrypt(byte[] key, byte[] input) throws GeneralSecurityException {
        // 把input分割成IV和密文:
        byte[] iv = new byte[16];
        byte[] data = new byte[input.length - 16];
        System.arraycopy(input, 0, iv, 0, 16); // IV
        System.arraycopy(input, 16, data, 0, data.length); //密文
        System.out.println(Arrays.toString(iv));
        // 解密:
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); // 密码对象
        SecretKeySpec keySpec = new SecretKeySpec(key, "AES"); // 恢复秘钥
        IvParameterSpec ivps = new IvParameterSpec(iv); // 恢复IV
        // 初始化秘钥:操作模式、秘钥、IV参数
        cipher.init(Cipher.DECRYPT_MODE, keySpec, ivps);
        // 解密操作
        return cipher.doFinal(data);
    }
    // 合并数组
    public static byte[] join(byte[] bs1, byte[] bs2) {
        byte[] r = new byte[bs1.length + bs2.length];
        System.arraycopy(bs1, 0, r, 0, bs1.length);
        System.arraycopy(bs2, 0, r, bs1.length, bs2.length);
        return r;
    }
}

import java.math.BigInteger;
import java.security.GeneralSecurityException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.KeyAgreement;
public class Main04 {
	public static void main(String[] args) {
        // Bob和Alice:
        Person bob = new Person("Bob");
        Person alice = new Person("Alice");
        // 各自生成KeyPair: 公钥+私钥
        bob.generateKeyPair();
        alice.generateKeyPair();
        // 双方交换各自的PublicKey(公钥):
        // Bob根据Alice的PublicKey生成自己的本地密钥(共享公钥):
        bob.generateSecretKey(alice.publicKey.getEncoded());
        // Alice根据Bob的PublicKey生成自己的本地密钥(共享公钥):
        alice.generateSecretKey(bob.publicKey.getEncoded());
        // 检查双方的本地密钥是否相同:
        bob.printKeys();
        alice.printKeys();
        // 双方的SecretKey相同，后续通信将使用SecretKey作为密钥进行AES加解密...
    }
}
// 用户类
class Person {
    public final String name; // 姓名
    // 密钥
    public PublicKey publicKey; // 公钥
    private PrivateKey privateKey; // 私钥
    private byte[] secretKey; // 本地秘钥(共享密钥)
    // 构造方法
    public Person(String name) {
        this.name = name;
    }
    // 生成本地KeyPair:(公钥+私钥)
    public void generateKeyPair() {
        try {
        	// 创建DH算法的“秘钥对”生成器
            KeyPairGenerator kpGen = KeyPairGenerator.getInstance("DH");
            kpGen.initialize(512);
            // 生成一个"密钥对"
            KeyPair kp = kpGen.generateKeyPair();
            this.privateKey = kp.getPrivate(); // 私钥
            this.publicKey = kp.getPublic(); // 公钥
        } catch (GeneralSecurityException e) {
            throw new RuntimeException(e);
        }
    }
    // 按照 "对方的公钥" => 生成"共享密钥"
    public void generateSecretKey(byte[] receivedPubKeyBytes) {
        try {
            // 从byte[]恢复PublicKey:
            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(receivedPubKeyBytes);
            // 根据DH算法获取KeyFactory
            KeyFactory kf = KeyFactory.getInstance("DH");
            // 通过KeyFactory创建公钥
            PublicKey receivedPublicKey = kf.generatePublic(keySpec);
            // 生成本地密钥(共享公钥)
            KeyAgreement keyAgreement = KeyAgreement.getInstance("DH");
            keyAgreement.init(this.privateKey); // 初始化"自己的PrivateKey"
            keyAgreement.doPhase(receivedPublicKey, true); // 根据"对方的PublicKey"
            // 生成SecretKey本地密钥(共享公钥)
            this.secretKey = keyAgreement.generateSecret();
        } catch (GeneralSecurityException e) {
            throw new RuntimeException(e);
        }
    }
    public void printKeys() {
        System.out.printf("Name: %s\n", this.name);
        System.out.printf("Private key: %x\n", new BigInteger(1, this.privateKey.getEncoded()));
        System.out.printf("Public key: %x\n", new BigInteger(1, this.publicKey.getEncoded()));
        System.out.printf("Secret key: %x\n", new BigInteger(1, this.secretKey));
    }
}

import java.math.BigInteger;
import java.security.GeneralSecurityException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import javax.crypto.Cipher;
// RSA
public class Main {
	public static void main(String[] args) throws Exception {
		// 明文:
		byte[] plain = "Hello, encrypt use RSA".getBytes("UTF-8");
		// 创建公钥／私钥对:
		Human alice = new Human("Alice");
		// 用Alice的公钥加密:
		// 获取Alice的公钥，并输出
		byte[] pk = alice.getPublicKey();
		System.out.println(String.fORMat("public key(公钥): %x", new BigInteger(1, pk)));
		// 使用公钥加密
		byte[] encrypted = alice.encrypt(plain);
		System.out.println(String.format("encrypted(加密): %x", new BigInteger(1, encrypted)));
		// 用Alice的私钥解密:
		// 获取Alice的私钥，并输出
		byte[] sk = alice.getPrivateKey();
		System.out.println(String.format("private key(私钥): %x", new BigInteger(1, sk)));
		// 使用私钥解密
		byte[] decrypted = alice.decrypt(encrypted);
		System.out.println("decrypted(解密): " + new String(decrypted, "UTF-8"));
	}
}
// 用户类
class Human {
	// 姓名
	String name;
	// 私钥:
	PrivateKey sk;
	// 公钥:
	PublicKey pk;
	// 构造方法
	public Human(String name) throws GeneralSecurityException {
		// 初始化姓名
		this.name = name;
		// 生成公钥／私钥对:
		KeyPairGenerator kpGen = KeyPairGenerator.getInstance("RSA");
		kpGen.initialize(1024);
		KeyPair kp = kpGen.generateKeyPair();
		this.sk = kp.getPrivate();
		this.pk = kp.getPublic();
	}
	// 把私钥导出为字节
	public byte[] getPrivateKey() {
		return this.sk.getEncoded();
	}
	// 把公钥导出为字节
	public byte[] getPublicKey() {
		return this.pk.getEncoded();
	}
	// 用公钥加密:
	public byte[] encrypt(byte[] message) throws GeneralSecurityException {
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.ENCRYPT_MODE, this.pk); // 使用公钥进行初始化
		return cipher.doFinal(message);
	}
	// 用私钥解密:
	public byte[] decrypt(byte[] input) throws GeneralSecurityException {
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, this.sk); // 使用私钥进行初始化
		return cipher.doFinal(input);
	}
}