原文

https://howtodoinjava.com/java/java-security/java-aes-encryption-example/
https://howtodoinjava.com/java/java-security/aes-256-encryption-decryption/

AES对称加密算法

是代替老旧的DES算法的高级加密算法，美国标准、安全性更高。
对称加密算法的性能比非对称加密算法的性能要高很多，因为对称加密是做计算机擅长的位运算，而非对称加密需要做大量的大数幂运算、加法运算、模运算，性能相差很大。

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.Base64;

public class AES {
    private static SecretKeySpec secretKey;
    private static byte[] key;

    public static void setKey(final String myKey) {
        MessageDigest sha = null;
        try {
            key = myKey.getBytes("UTF-8");
            sha = MessageDigest.getInstance("SHA-1");
            key = sha.digest(key);
            key = Arrays.copyOf(key, 16);
            secretKey = new SecretKeySpec(key, "AES");
        } catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
            e.printStackTrace();
        }
    }

    public static String encrypt(final String strToEncrypt, final String secret) {
        try {
            setKey(secret);
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, secretKey);
            return Base64.getEncoder()
                    .encodeToString(cipher.doFinal(strToEncrypt.getBytes("UTF-8")));
        } catch (Exception e) {
            System.out.println("Error while encrypting: " + e.toString());
        }
        return null;
    }

    public static String decrypt(final String strToDecrypt, final String secret) {
        try {
            setKey(secret);
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");
            cipher.init(Cipher.DECRYPT_MODE, secretKey);
            return new String(cipher.doFinal(Base64.getDecoder()
                    .decode(strToDecrypt)));
        } catch (Exception e) {
            System.out.println("Error while decrypting: " + e.toString());
        }
        return null;
    }

    public static void main(String[] args) {
        final String secretKey = "ssshhhhhhhhhhh!!!!";

        String originalString = "howtodoinjava.com";
        String encryptedString = AES.encrypt(originalString, secretKey) ;
        String decryptedString = AES.decrypt(encryptedString, secretKey) ;

        System.out.println("明文：" + originalString);
        System.out.println("密文：" + encryptedString);
        System.out.println("解密后明文：" + decryptedString);
    }
}