Java中基于AES-256密码的加密/解密

Posted 2023-02-16

【中文标题】Java中基于AES-256密码的加密/解密

【英文标题】：AES-256 Password Based Encryption/Decryption in Java

【发布时间】：2015-04-21 17:54:02

【问题描述】：

我找到了在 Java 中实现 AES 加密/解密的指南，并在我将其放入自己的解决方案时尝试理解每一行。但是，我并不完全理解它，因此遇到了问题。最终目标是拥有基于密码的加密/解密。我已阅读有关此的其他文章/*** 帖子，但大多数都没有提供足够的解释（我对 Java 中的加密非常陌生）

我现在的主要问题是即使我设置了byte[] saltBytes = "Hello".getBytes(); 最后我仍然得到不同的 Base64 结果（char[] password 每次都是随机的，但我读到以char[] 形式留下密码更安全。我的另一个问题是当程序到达decrypt() 时，我在获得 NullPointerException byte[] saltBytes = salt.getBytes("UTF-8");

提前感谢您能给我的任何帮助/建议。

有问题的代码：

import java.security.AlgorithmParameters;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.bind.DatatypeConverter;

public class EncryptionDecryption 

    private static String salt;
    private static int iterations = 65536  ;
    private static int keySize = 256;
    private static byte[] ivBytes;

    public static void main(String []args) throws Exception 

        char[] message = "PasswordToEncrypt".toCharArray();
        System.out.println("Message: " + message.toString());
        System.out.println("Encrypted: " + encrypt(message));
        System.out.println("Decrypted: " + decrypt(encrypt(message).toCharArray()));
    

    public static String encrypt(char[] plaintext) throws Exception 

        salt = getSalt();
        byte[] saltBytes = salt.getBytes();

        SecretKeyFactory skf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        PBEKeySpec spec = new PBEKeySpec(plaintext, saltBytes, iterations, keySize);
        SecretKey secretKey = skf.generateSecret(spec);
        SecretKeySpec secretSpec = new SecretKeySpec(secretKey.getEncoded(), "AES");

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretSpec);
        AlgorithmParameters params = cipher.getParameters();
        ivBytes = params.getParameterSpec(IvParameterSpec.class).getIV();
        byte[] encryptedTextBytes = cipher.doFinal(plaintext.toString().getBytes("UTF-8"));

        return DatatypeConverter.printBase64Binary(encryptedTextBytes);
    

    public static String decrypt(char[] encryptedText) throws Exception 

        byte[] saltBytes = salt.getBytes("UTF-8");
        byte[] encryptedTextBytes = DatatypeConverter.parseBase64Binary(encryptedText.toString());

        SecretKeyFactory skf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        PBEKeySpec spec = new PBEKeySpec(encryptedText, saltBytes, iterations, keySize);
        SecretKey secretkey = skf.generateSecret(spec);
        SecretKeySpec secretSpec = new SecretKeySpec(secretkey.getEncoded(), "AES");

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, secretSpec, new IvParameterSpec(ivBytes));

        byte[] decryptedTextBytes = null;

        try 
            decryptedTextBytes = cipher.doFinal(encryptedTextBytes);
           catch (IllegalBlockSizeException e) 
            e.printStackTrace();
           catch (BadPaddingException e) 
            e.printStackTrace();
        

        return decryptedTextBytes.toString();

    

    public static String getSalt() throws Exception 

        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
        byte[] salt = new byte[20];
        sr.nextBytes(salt);
        return salt.toString();
    

【参考方案1】：

我认为你犯了两个错误:)

我已更正您的示例代码以使其正常工作：

import java.security.AlgorithmParameters;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.bind.DatatypeConverter;

public class EncryptionDecryption 

    private static String salt;
    private static int iterations = 65536  ;
    private static int keySize = 256;
    private static byte[] ivBytes;

    private static SecretKey secretKey;

    public static void main(String []args) throws Exception 

        salt = getSalt();

        char[] message = "PasswordToEncrypt".toCharArray();
        System.out.println("Message: " + String.valueOf(message));
        System.out.println("Encrypted: " + encrypt(message));
        System.out.println("Decrypted: " + decrypt(encrypt(message).toCharArray()));
    

    public static String encrypt(char[] plaintext) throws Exception 
        byte[] saltBytes = salt.getBytes();

        SecretKeyFactory skf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        PBEKeySpec spec = new PBEKeySpec(plaintext, saltBytes, iterations, keySize);
        secretKey = skf.generateSecret(spec);
        SecretKeySpec secretSpec = new SecretKeySpec(secretKey.getEncoded(), "AES");

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretSpec);
        AlgorithmParameters params = cipher.getParameters();
        ivBytes = params.getParameterSpec(IvParameterSpec.class).getIV();
        byte[] encryptedTextBytes = cipher.doFinal(String.valueOf(plaintext).getBytes("UTF-8"));

        return DatatypeConverter.printBase64Binary(encryptedTextBytes);
    

    public static String decrypt(char[] encryptedText) throws Exception 

        System.out.println(encryptedText);

        byte[] encryptedTextBytes = DatatypeConverter.parseBase64Binary(new String(encryptedText));
        SecretKeySpec secretSpec = new SecretKeySpec(secretKey.getEncoded(), "AES");

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, secretSpec, new IvParameterSpec(ivBytes));

        byte[] decryptedTextBytes = null;

        try 
            decryptedTextBytes = cipher.doFinal(encryptedTextBytes);
           catch (IllegalBlockSizeException e) 
            e.printStackTrace();
           catch (BadPaddingException e) 
            e.printStackTrace();
        

        return new String(decryptedTextBytes);

    

    public static String getSalt() throws Exception 

        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
        byte[] salt = new byte[20];
        sr.nextBytes(salt);
        return new String(salt);
    

第一个错误是您生成了 2 个不同的盐（使用 encrypt 方法时），因此加密/解密的日志是不同的（合乎逻辑，但解密仍然有效，因为您在加密后直接调用解密）。

第二个错误是密钥。加密时需要生成密钥，但不解密时需要生成密钥。更简单地说，就好像我正在使用密码“encrypt”进行加密，而您正在尝试使用密码“decrypt”对其进行解密。

我建议您在启动时生成每个随机的东西（例如私钥、盐等）。但请注意，当您停止应用时，您将无法解密旧内容，除非得到完全相同的随机内容。

希望我能帮上忙:)

问候，

【讨论】：

DatatypeConverter 现在不支持了？

你能帮我按照这个命令修改你的代码openssl aes-128-cbc -a -e -in hello.txt -md sha256。我使用密码作为“通行证”。这个命令工作正常，但我得到的代码是Exception in thread "main" java.security.InvalidKeyException: Invalid AES key length: 4 bytes at com.sun.crypto.provider.AESCrypt.init(AESCrypt.java:87)