前言
本篇简单介绍下非对称加密以及公钥和私钥加密不同的使用场景，以及如何用Java代码实现AES加解密的工具类和例子
非对称加密简介
需要两个密钥（公钥和私钥）来进行加密和解密，公开密钥（public key，简称公钥）和私有密钥（private key，简称私钥） ，公钥加密的信息只有私钥才能解开，私钥加密的信息只有公钥才能解开。这个公钥和私钥必须是一对的，如果用公钥对数据进行加密，那么只有使用对应的私钥才能解密，所以只要私钥不泄露，那么我
- 对于签名：私钥加密，公钥解密。好比你的签名只有你自已签的才是真的，别人签的都是假的。
们的数据就是安全的。
公钥加密或私钥加密
- 对于加密：公钥加密，私钥加密。毕竟公钥可以公开，但是私钥只有你自已知道，你也同样希望只有你自已才能解密
- 对于签名：私钥加密，公钥解密。好比你的签名只有你自已签的才是真的，别人签的都是假的。
Java实现常用的AES非对称加解密工具类
RSA 算法是非对称加解密中比较常用的加密算法，基于一个十分简单的数论事实：将两个大素数相乘十分容易，但是想要对其乘积进行因式分解却极其困难，因此可以将乘积公开作为加密密钥。
在加载的时候PKCS#1 format的私钥的时候，可能会报错，需要加如下maven依赖，我在代码里loadPrivateKey也有说明
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk15on</artifactId>
<version>1.58</version>
</dependency>
下面直接上干货，测试代码，写在main方法里了，其他说明写在注释里。
如有需要Javascript版本的RSA加解密，请看 https://blog.terrynow.com/2021/04/20/javascript-tool-rsa-encrypt-implement/
RSAUtil.java
package com.terrynow.test;
import javax.crypto.Cipher;
import java.nio.charset.StandardCharsets;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
/**
* @author Terry E-mail: yaoxinghuo at 126 dot com
* @date 2021-4-14 10:51
* @description
*/
public class RSAUtil {
public static void main(String[] args) throws Exception {
PrivateKey privateKey = loadPrivateKey("-----BEGIN RSA PRIVATE KEY-----\n" +
"MIICeAIBADANBgkqhkiG9w0BAQEFAASCAmIwggJeAgEAAoGBAJlTlMmhFxhVZ/U6xd3\n" +
"TZTelu0g8a+tZYAqoOegsJXXlelthlLTzx5qkWEf4STjIMaIYtduIO1xVs1L3Gsjyl3\n" +
"IhofjuVwI2qk2QVCtuVXkDvO/gPXCzur5iTDCG7Jrh5jJI5VtaVGHVH37TSWUYiowKv\n" +
"SzdKViPQ1h1J/BPewI5AgMBAAECgYAwBq4kOgEx7g6SEcbIpN6ff5oaFlL3dRdQP0Fk\n" +
"J+/T7f1VgktCItny5meAo5TL5GknjPXpvdJaKb3xztTk/JfS+X4uZBuEumb+UV8hWzJ\n" +
"0hvxIMtVf0rwFLbEB6btiNJHDCIv2+eJSEoK2RjYF/qGb0zzFz1YGICY5Vjl2TDnlwQ\n" +
"JBAPHbqEWKT1KeEXKzNBcZadglfjF+qXQmWFGN3yUrd8Xxmet+oKfhXgPgybfo8/uwM\n" +
"6ijJaEYNWWU6wbvMf9jkZ8CQQCiSrTLyzEe9pObKpwGk3U2jkaYOnSKdMYebxvF9BGN\n" +
"CnLsen0rDOefgHGNwUMphzWaqWESnb1TB7Mck/kanU0nAkEA3D1Zg1HKoAI/A0L62Vo\n" +
"UD3c87hdYeeN9I27c1/04SXGT52XdKGNKeJ+XMTkaDITM1fETEBp6bXFpgFwLHHRwIw\n" +
"JBAKExPFOyNM7BMCiM8L2jVmdidwGaBcjDZUgzKU27Nnd06mKw4oOQ5LnKtH6Mdy3XK\n" +
"sm79DuuSq4eVqtK2b+yfz8CQQC7frRjmYPe9+2JrTWMbzfFlLysCn7xmdbW5rVCs8sO\n" +
"5jq8YxW5nV99IVGaKjYw6wcjIGut9uZw6Mmec05CODzh\n" +
"-----END RSA PRIVATE KEY-----");
PublicKey publicKey = loadPublicKey("-----BEGIN PUBLIC KEY-----\n" +
"MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCZU5TJoRcYVWf1OsXd02U3pbtIPGv\n" +
"rWWAKqDnoLCV15XpbYZS088eapFhH+Ek4yDGiGLXbiDtcVbNS9xrI8pdyIaH47lcCNq\n" +
"pNkFQrblV5A7zv4D1ws7q+Ykwwhuya4eYySOVbWlRh1R9+00llGIqMCr0s3SlYj0NYd\n" +
"SfwT3sCOQIDAQAB\n" +
"-----END PUBLIC KEY-----");
// KeyPair keyPair = buildKeyPair();
// String privateString = base64Encode(keyPair.getPrivate().getEncoded());
// String publicString = base64Encode(keyPair.getPublic().getEncoded());
// System.out.println("private:");
// System.out.println(privateString);
// System.out.println("public:");
// System.out.println(publicString);
byte[] encrypted = encrypt(publicKey, "This is a test!");
System.out.println(base64Encode(encrypted));
byte[] bytes = decrypt(privateKey, base64Decode("VX1x8DRvRyvklwXPCXzUgg7eZx7j8wQ2ZdwLSv68rHIk4PAkdwXvk+7WHgG8R27Xq8u2Q/5V6Yrji43EqD7b02JjjYlN1XbfjiJvP4HoBR8yTgjOrhXBd3N+fIhEl6B7CYCaEVdQtL32q7x+CKDIlZbnTt1E3ofCtAc17/H8m8s="));
System.out.println(new String(bytes));
}
public static final String RSA_ALGORITHM = "RSA";
/**
* 成功密钥对
*/
public static KeyPair buildKeyPair() throws NoSuchAlgorithmException {
final int keySize = 1024;
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(RSA_ALGORITHM);
keyPairGenerator.initialize(keySize);
return keyPairGenerator.genKeyPair();
}
/**
* 用私钥加密
*/
public static byte[] encrypt(PrivateKey privateKey, String message) throws Exception {
Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, privateKey);
return cipher.doFinal(message.getBytes(StandardCharsets.UTF_8));
}
/**
* 用公钥加密
*/
public static byte[] encrypt(PublicKey publicKey, String message) throws Exception {
Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return cipher.doFinal(message.getBytes(StandardCharsets.UTF_8));
}
/**
* 用公钥解密
*/
public static byte[] decrypt(PublicKey publicKey, byte[] encrypted) throws Exception {
Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, publicKey);
return cipher.doFinal(encrypted);
}
/**
* 用私钥解密
*/
public static byte[] decrypt(PrivateKey privateKey, byte[] encrypted) throws Exception {
Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return cipher.doFinal(encrypted);
}
/**
* 从文本中加载公钥
*/
public static PublicKey loadPublicKey(String publicKeyStr) throws Exception {
String string = publicKeyStr
.replace("-----BEGIN PUBLIC KEY-----", "")
.replace("-----END PUBLIC KEY-----", "")
.replaceAll("\\s", "");
byte[] buffer = base64Decode(string);
KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
return keyFactory.generatePublic(keySpec);
}
/**
* 从文本中加载私钥
*/
public static PrivateKey loadPrivateKey(String privateKeyStr) throws Exception {
// PKCS#1 format 格式的私钥会报错，需要假如如下addProvider，maven需要添加如下dependency
// <dependency>
// <groupId>org.bouncycastle</groupId>
// <artifactId>bcprov-jdk15on</artifactId>
// <version>1.58</version>
// </dependency>
java.security.Security.addProvider(
new org.bouncycastle.jce.provider.BouncyCastleProvider()
);
String string = privateKeyStr
.replace("-----BEGIN RSA PRIVATE KEY-----", "")
.replace("-----END RSA PRIVATE KEY-----", "")
.replace("-----BEGIN PRIVATE KEY-----", "")
.replace("-----END PRIVATE KEY-----", "")
.replaceAll("\\s", "");
byte[] buffer = base64Decode(string);
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
return keyFactory.generatePrivate(keySpec);
}
public static String base64Encode(byte[] data) {
return Base64.getEncoder().encodeToString(data);
}
public static byte[] base64Decode(String data) {
return Base64.getDecoder().decode(data);
}
}
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