Java中基于AES-256密码的加密/解密

AES-256 Password Based Encryption/Decryption in Java(Java中基于AES-256密码的加密/解密)

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/stackoverflow 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)

I found a guide for implementing AES encryption/decryption in Java and tried to understand each line as I put it into my own solution. However, I don't fully understand it and am having issues as a result. The end goal is to have passphrase based encryption/decryption. I've read other articles/stackoverflow posts about this, but most do not provide enough explanation (I am very new to crypto in Java)

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byte[] saltBytes = salt.getBytes("UTF-8");

My main issues right now are that even when I set byte[] saltBytes = "Hello".getBytes(); I still get a different Base64 result in the end (char[] password is random each time, but I read that it is safer to leave passwords in char[] form. My other problem is that when the program gets to decrypt(), I get a NullPointerException at byte[] saltBytes = salt.getBytes("UTF-8");

提前感谢您能给我的任何帮助/建议.

Thank you in advance for any help/advice you can give me.

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();
    }
}

推荐答案

我认为你犯了两个错误:)

I think that you are making two mistakes :)

我已更正您的示例代码以使其正常工作:

I've corrected your sample code to make it work :

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).

The first mistake is that you generate 2 different salts (when using the encrypt method), so encrypted/decrypted logs were differents (logical, but the decryption would still work because you are calling the decryption directly after encryption).

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.

The second mistake was for the secret key. You need to generate a secret key when you are encrypting, but not decrypting. To put it more simply, it is as if i was encrypting with the password "encrypt" and that you are trying to decrypt it with the password "decrypt".

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.

I would advise you to generate every random stuff (such as private key, salt etc on startup). But beware that when you'll stop your app, you won't be able to decrypt old stuff unless getting the exact same random stuff.

希望我能帮上忙:)

问候，

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