aes cbc demo

AesDemo.java

package com.honey;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.util.Base64;
import java.util.Random;

public class AesDemo {

    private static final Random RANDOM = new Random(System.currentTimeMillis());
    public static void main(String[] args) throws Exception {
        String key = randomKey();
        String iv = randomKey();
        System.out.println("AES/CBC/PKCS5Padding");
        System.out.println("key=" + key + ",iv=" + iv);
        String content = "you can't see me!";
        String encrypted = encrypt(content, key, iv);
        String decrypted = decrypt(encrypted, key, iv);
        System.out.println("encrypted=" + encrypted + ",decrypted=" + decrypted);
    }

    private static String randomKey() {
        String origin = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "abcdefghijklmnopqrstuvwxyz" + "1234567890";
        StringBuilder sb = new StringBuilder(16);
        for (int i = 0; i < 16; i++) {
            int idx = RANDOM.nextInt(26 + 26 + 10);
            sb.append(origin.charAt(idx));
        }
        return sb.toString();
    }

    //加密
    public static String encrypt(String content, String key, String iv) throws Exception {
        byte[] raw = key.getBytes("utf-8");
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");//"算法/模式/补码方式"
        //使用CBC模式，需要一个向量iv，可增加加密算法的强度
        IvParameterSpec ips = new IvParameterSpec(iv.getBytes());
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, ips);
        byte[] encrypted = cipher.doFinal(content.getBytes());
        return Base64.getEncoder().encodeToString(encrypted);
    }


    //解密
    public static String decrypt(String content, String key, String iv) throws Exception {
        try {
            byte[] raw = key.getBytes("utf-8");
            SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            IvParameterSpec ips = new IvParameterSpec(iv.getBytes());
            cipher.init(Cipher.DECRYPT_MODE, skeySpec, ips);
            byte[] encrypted = Base64.getDecoder().decode(content);
            try {
                byte[] original = cipher.doFinal(encrypted);
                String originalString = new String(original, StandardCharsets.UTF_8);
                return originalString;
            } catch (Exception e) {
                System.err.println(e.toString());
                return null;
            }
        } catch (Exception ex) {
            System.err.println(ex.toString());
            return null;
        }
    }
}
///
/// one result example
///
AES/CBC/PKCS5Padding
key=0oaJ3WwHV1me3NwL,iv=DhlQ9sIG3i5Q7R0d
encrypted=tEglOFwLnnaZUlJdh6mQPtJh6xSbmlQ5iutCg6x6QB4=,decrypted=you can't see me!
///
/// for checking online
/// see http://ctf.ssleye.com/caes.html
/// img: https://wx1.sinaimg.cn/mw1024/667f4ad7ly1g82unnwe6xj21iz0u0adz.jpg

///