1. AES

1.1. 概念

密码学中的高级加密标准（Advanced Encryption Standard，AES），又称Rijndael加密法，是美国联邦政府采用的一种区块加密标准。
这个标准用来替代原先的DES（Data Encryption Standard），已经被多方分析且广为全世界所使用，已然成为对称密钥加密中最流行的算法之一。详见 百科 高级加密标准 AES

1.2. JAVA实现AES加解密

import lombok.extern.slf4j.Slf4j;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;
import java.util.Arrays;

@Slf4j
class AESCryptoUtil {
    
    public static void main(String[] args) {
    
        String content = "美好的世界,美好的中国,美好的未来！！！";

        byte[] encryptResult = encrypt(content);
        byte[] decryptResult = decrypt(encryptResult);


        String encryptStr = parseByte2HexStr(encryptResult);
        printMsg("========\n加密前:%s\n加密后:%s\n解密后：%s", content, encryptStr, new String(decryptResult));

        //解密时，不能new String(encryptResult,"utf-8").getBytes("utf-8")
        decryptResult = decrypt(parseHexStr2Byte(encryptStr));
        printMsg("========\n加密前:%s\n加密后:%s\n解密后：%s", content, encryptStr,new String(decryptResult));


        //采用AES/ECB/NoPadding时，要求密钥长度16、24、32中的一个、待加密内容的byte[]长度必须是16的倍数
        encryptResult = encrypt2(content);
        decryptResult = decrypt2(encryptResult);
        encryptStr = parseByte2HexStr(encryptResult);
        printMsg("========\n加密前:%s\n加密后:%s\n解密后：%s", content, encryptStr, new String(decryptResult));

    }

    private static void printMsg(String template, Object... args) {
    
        System.out.println(String.format(template, args));
    }

    private static String password = "科技兴国@！##";
    private static SecretKeySpec key;

    static {
    
        init();
    }

    private static void init() {
    
        try {
    
            KeyGenerator kgen = KeyGenerator.getInstance("AES");
            kgen.init(256, new SecureRandom(password.getBytes()));
            SecretKey secretKey = kgen.generateKey();
            byte[] enCodeFormat = secretKey.getEncoded();
            key = new SecretKeySpec(enCodeFormat, "AES");
        } catch (Exception e) {
    
            log.error("初始化AES算法失败" + e.getMessage(), e);
        }
    }

    /**
     * 加密
     *
     * @param content 需要加密的内容
     * @return
     */
    public static byte[] encrypt(String content) {
    
        try {
    
            Cipher cipher = Cipher.getInstance("AES");
            byte[] byteContent = content.getBytes("utf-8");
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byte[] result = cipher.doFinal(byteContent);
            return result;
        } catch (Exception e) {
    
            log.error("AES加密失败" + e.getMessage(), e);
        }
        return null;
    }

    public static byte[] decrypt(byte[] content) {
    
        try {
    
            Cipher cipher = Cipher.getInstance("AES");
            cipher.init(Cipher.DECRYPT_MODE, key);
            byte[] result = cipher.doFinal(content);
            return result;
        } catch (Exception e) {
    
            log.error("AES解密失败" + e.getMessage(), e);
        }
        return null;
    }

    /**
     * 加密
     *
     * @param content 需要加密的内容
     * @return
     */
    public static byte[] encrypt2(String content) {
    
        try {
    
            byte[] bytePassword = password.getBytes();
            bytePassword = checkByteLength(bytePassword);
            SecretKeySpec key = new SecretKeySpec(bytePassword, "AES");
            Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
            byte[] byteContent = content.getBytes("utf-8");
            byteContent = checkByteLength(byteContent);
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byte[] result = cipher.doFinal(byteContent);
            return result;
        } catch (Exception e) {
    
            log.error("AES加密失败" + e.getMessage(), e);
        }
        return null;
    }

    public static byte[] decrypt2(byte[] content) {
    
        try {
    
            byte[] bytePassword = password.getBytes();
            bytePassword = checkByteLength(bytePassword);
            SecretKeySpec key = new SecretKeySpec(bytePassword, "AES");
            Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
            cipher.init(Cipher.DECRYPT_MODE, key);
            byte[] result = cipher.doFinal(content);
            return result;
        } catch (Exception e) {
    
            log.error("AES解密失败" + e.getMessage(), e);
        }
        return null;
    }

    private static byte[] checkByteLength(byte[] byteContent) {
    
        int length = byteContent.length;
        int remainder = length % 16;
        if(remainder == 0){
    
            return byteContent;
        }else{
    
            return Arrays.copyOf(byteContent,length+(16-remainder));
        }
    }

    /**将二进制转换成16进制
     * @param buf
     * @return
     */
    public static String parseByte2HexStr(byte buf[]) {
    
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < buf.length; i++) {
    
            String hex = Integer.toHexString(buf[i] & 0xFF);
            if (hex.length() == 1) {
    
                hex = '0' + hex;
            }
            sb.append(hex.toUpperCase());
        }
        return sb.toString();
    }

    public static byte[] parseHexStr2Byte(String hexStr) {
    
        if (hexStr.length() < 1) {
    
            return null;
        }
        byte[] result = new byte[hexStr.length()/2];
        for (int i = 0;i< hexStr.length()/2; i++) {
    
            int high = Integer.parseInt(hexStr.substring(i*2, i*2+1), 16);
            int low = Integer.parseInt(hexStr.substring(i*2+1, i*2+2), 16);
            result[i] = (byte) (high * 16 + low);
        }
        return result;
    }
}

2. 使用中的各种坑

2.1. 加密后的byte数组不能强制转换成字符串

加密后返回byte[]，此byte数组强制转换为字符串是乱码，然后再用转换后的字符串转换为byte数组去解码（见下面的代码）会报错：Input length must be multiple of 16 when decrypting with padded cipher

在这种情况下: 字符串和byte数组不是互逆的；要避免这种情况，需要做一些修订，可以考虑将二进制数据转换成十六进制表示。详见parseByte2HexStr、parseHexStr2Byte两个方法

decryptResult = decrypt(new String(encryptResult,"utf-8").getBytes("utf-8"));

2021-07-02 11:27:39.067 [main] ERROR pattern.chain.AESCryptoUtil:decrypt:87 - AES解密失败Input length must be multiple of 16 when decrypting with padded cipher
javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:936) ~[sunjce_provider.jar:1.8.0_171]
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:847) ~[sunjce_provider.jar:1.8.0_171]
at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:446) ~[sunjce_provider.jar:1.8.0_171]
at javax.crypto.Cipher.doFinal(Cipher.java:2164) ~[?:1.8.0_171]
at org.apache.design.pattern.chain.AESCryptoUtil.decrypt(AESCryptoUtil.java:84) [classes/:?]
at org.apache.design.pattern.chain.AESCryptoUtil.main(AESCryptoUtil.java:26) [classes/:?]

2.2. 采用AES/ECB/NoPadding加密的限制

当采用如下方式获取Cipher实例时，则要求密钥长度16、24、32中的一个、待加密内容的byte[]长度必须是16的倍数，否则报如下错误:

Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");

2021-07-02 11:37:15.432 [main] ERROR pattern.chain.AESCryptoUtil:encrypt2:111 - AES加密失败Input length not multiple of 16 bytes
javax.crypto.IllegalBlockSizeException: Input length not multiple of 16 bytes
at com.sun.crypto.provider.CipherCore.finalNoPadding(CipherCore.java:1042) ~[sunjce_provider.jar:1.8.0_171]
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:1010) ~[sunjce_provider.jar:1.8.0_171]
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:847) ~[sunjce_provider.jar:1.8.0_171]
at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:446) ~[sunjce_provider.jar:1.8.0_171]
at javax.crypto.Cipher.doFinal(Cipher.java:2164) ~[?:1.8.0_171]

或
2021-07-02 11:36:39.064 [main] ERROR pattern.chain.AESCryptoUtil:encrypt2:111 - AES加密失败Invalid AES key length: 18 bytes
java.security.InvalidKeyException: Invalid AES key length: 18 bytes
at com.sun.crypto.provider.AESCrypt.init(AESCrypt.java:87) ~[sunjce_provider.jar:1.8.0_171]
at com.sun.crypto.provider.ElectronicCodeBook.init(ElectronicCodeBook.java:94) ~[sunjce_provider.jar:1.8.0_171]
at com.sun.crypto.provider.CipherCore.init(CipherCore.java:592) ~[sunjce_provider.jar:1.8.0_171]
at com.sun.crypto.provider.CipherCore.init(CipherCore.java:468) ~[sunjce_provider.jar:1.8.0_171]
at com.sun.crypto.provider.AESCipher.engineInit(AESCipher.java:313) ~[sunjce_provider.jar:1.8.0_171]
at javax.crypto.Cipher.implInit(Cipher.java:801) ~[?:1.8.0_171]
at javax.crypto.Cipher.chooseProvider(Cipher.java:863) ~[?:1.8.0_171]

2.3 美国的出口管制限制引起的坑

2.3.1. 背景

因为美国的出口管制限制，Java发布的运行环境包中的加解密有一定的限制。
比如默认不允许256位密钥的AES加解密，如果使用，会报如下错误:
2021-07-02 11:40:34.048 [main] ERROR pattern.chain.AESCryptoUtil:encrypt:75 - AES加密失败Illegal key size or default parameters
java.security.InvalidKeyException: Illegal key size or default parameters
at javax.crypto.Cipher.checkCryptoPerm(Cipher.java:1025) ~[?:1.8.0_171]
at javax.crypto.Cipher.implInit(Cipher.java:800) ~[?:1.8.0_171]
at javax.crypto.Cipher.chooseProvider(Cipher.java:863) ~[?:1.8.0_171]
at javax.crypto.Cipher.init(Cipher.java:1248) ~[?:1.8.0_171]
at javax.crypto.Cipher.init(Cipher.java:1185) ~[?:1.8.0_171]

从Java 1.8.0_151

2.3.2. 解决方案

方案1
将%JDK_HOME%\jre\lib\security\java.security, 找到定义java安全性属性crypto.policy的行，将值修改为unlimited。
默认情况下，您应该能找到一条注释掉的行：
#crypto.policy=unlimited
您可以通过取消注释该行来启用无限制，删除＃：

方案2
如果%JDK_HOME%\jre\lib\security目录下有jar包 且 crypto.policy 未配置，则使用jar包内置的规则
将%JDK_HOME%\jre\lib\security\policy\unlimited下的2个JAR【local_policy.jar、US_export_policy.jar】复制到%JDK_HOME%\jre\lib\security目录下，如果有，直接覆盖。

方案3
如果%JDK_HOME%\jre\lib\security目录下没有jar包 且 crypto.policy 未配置，则默认启用无限制的。

升级版本
https://www.oracle.com/technetwork/java/javase/8u161-relnotes-4021379.html
在官方文档写到，
security-libs/javax.crypto
Unlimited cryptography enabled by default
The JDK uses the Java Cryptography Extension (JCE) Jurisdiction Policy files to configure cryptographic algorithm restrictions. Previously, the Policy files in the JDK placed limits on various algorithms. This release ships with both the limited and unlimited jurisdiction policy files, with unlimited being the default. The behavior can be controlled via the new ‘crypto.policy’ Security property found in the /lib/java.security file. Please refer to that file for more information on this property.
也就是从 1.8.0_161-b12 版本后，默认将采用无限制的加密算法，也就是使用 unlimited 下的jar包。我们也可以通过 设置 java.security 文件的 crypto.policy的值来改变这个默认的值。