Java中基于AES-256密码的加密/解密

Question

我找到了用Java实施AES加密/解密的指南，并试图理解每一行并将其放入自己的解决方案中。但是，我没有完全理解它，因此出现了问题。最终目标是拥有基于密码的加密/解密。我已经阅读了有关此的其他文章/
stackoverflow帖子，但是大多数文章没有提供足够的解释（我对Java加密非常陌生）

我现在的主要问题是，即使设置了byte[] saltBytes = "Hello".getBytes();
I，最后还是会得到不同的Base64结果（char[] password每次都是随机的，但是我读到将密码保留在char[]窗体中是更安全的。我的另一个问题是，当程序进入decrypt()，我得到一个NullPointerException
byte[] saltBytes = salt.getBytes("UTF-8");

预先感谢您可以给我的任何帮助/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();
    }
}

Answer 1

我认为您犯了两个错误:)

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2种不同的盐（使用加密方法时），因此加密/解密的日志是不同的（逻辑上，但是解密仍然有效，因为您在加密后立即调用解密）。

第二个错误是密钥。在加密而不是解密时，需要生成一个秘密密钥。简而言之，好像我正在使用密码“ encrypt”进行加密一样，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所有随机的东西（例如私钥，盐等）。但要注意，当您停止应用程序时，除非获得完全相同的随机内容，否则您将无法解密旧内容。

希望我能帮到:)

问候，