android sharedmemory 怎样进行数据解密

Android SharedMemory 本身并不提供加密和解密功能。但是，你可以在将数据写入 SharedMemory 之前进行加密，并在从 SharedMemory 读取数据后进行解密。这可以通过使用对称加密算法（如 AES）来实现。

以下是一个简单的示例，展示了如何使用 AES 加密和解密数据：

首先，确保你已经在项目中添加了 AES 库。在 build.gradle 文件中添加以下依赖：

implementation 'com.google.crypto:crypto-js:4.1.1'

创建一个加密和解密函数：

import com.google.crypto.Cipher;
import com.google.crypto.spec.IvParameterSpec;
import com.google.crypto.spec.SecretKeySpec;
import org.json.JSONObject;

import java.nio.charset.StandardCharsets;
import java.util.Base64;

public class AESUtil {
    private static final String AES_ALGORITHM = "AES/CBC/PKCS5Padding";
    private static final String AES_KEY = "your-secret-key"; // 请替换为你的密钥
    private static final String AES_IV = "your-initial-vector"; // 请替换为你的初始向量

    public static String encrypt(String data) throws Exception {
        SecretKeySpec secretKeySpec = new SecretKeySpec(AES_KEY.getBytes(StandardCharsets.UTF_8), AES_ALGORITHM);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(AES_IV.getBytes(StandardCharsets.UTF_8));
        Cipher cipher = Cipher.getInstance(AES_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] encryptedBytes = cipher.doFinal(data.getBytes(StandardCharsets.UTF_8));
        return Base64.getEncoder().encodeToString(encryptedBytes);
    }

    public static String decrypt(String encryptedData) throws Exception {
        SecretKeySpec secretKeySpec = new SecretKeySpec(AES_KEY.getBytes(StandardCharsets.UTF_8), AES_ALGORITHM);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(AES_IV.getBytes(StandardCharsets.UTF_8));
        Cipher cipher = Cipher.getInstance(AES_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(encryptedData));
        return new String(decryptedBytes, StandardCharsets.UTF_8);
    }
}

使用加密和解密函数处理 SharedMemory 中的数据：

import android.os.Build;
import android.os.Environment;
import android.os.storage.FileChannel;
import android.os.storage.StorageManager;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileLock;
import java.nio.channels.OverlappingFileLockException;

public class SharedMemoryManager {
    private static final String SHARED_MEMORY_FILE_PATH = Environment.getExternalStorageDirectory().getAbsolutePath() + "/shared_memory.dat";

    public static void writeEncryptedDataToSharedMemory(String data) throws Exception {
        String encryptedData = AESUtil.encrypt(data);
        File sharedMemoryFile = new File(SHARED_MEMORY_FILE_PATH);
        if (!sharedMemoryFile.exists()) {
            sharedMemoryFile.createNewFile();
        }
        try (FileOutputStream fos = new FileOutputStream(sharedMemoryFile);
             FileChannel fileChannel = fos.getChannel()) {
            FileLock lock = null;
            try {
                lock = fileChannel.tryLock();
                if (lock != null) {
                    try {
                        fos.write(encryptedData.getBytes(StandardCharsets.UTF_8));
                    } finally {
                        lock.release();
                    }
                }
            } finally {
                if (lock != null) {
                    lock.release();
                }
            }
        }
    }

    public static String readEncryptedDataFromSharedMemory() throws Exception {
        File sharedMemoryFile = new File(SHARED_MEMORY_FILE_PATH);
        if (!sharedMemoryFile.exists()) {
            return null;
        }
        StringBuilder encryptedData = new StringBuilder();
        try (FileInputStream fis = new FileInputStream(sharedMemoryFile);
             FileChannel fileChannel = fis.getChannel()) {
            FileLock lock = null;
            try {
                lock = fileChannel.tryLock();
                if (lock != null) {
                    try {
                        int bytesRead;
                        byte[] buffer = new byte[1024];
                        while ((bytesRead = fis.read(buffer)) != -1) {
                            encryptedData.append(new String(buffer, 0, bytesRead, StandardCharsets.UTF_8));
                        }
                    } finally {
                        lock.release();
                    }
                }
            } finally {
                if (lock != null) {
                    lock.release();
                }
            }
        }
        return encryptedData.toString();
    }

    public static String decryptSharedMemoryData() throws Exception {
        String encryptedData = readEncryptedDataFromSharedMemory();
        return AESUtil.decrypt(encryptedData);
    }
}

请注意，这个示例仅用于演示目的。在实际应用中，你需要考虑更多的安全因素，例如密钥管理和存储、初始向量的安全性等。此外，由于 SharedMemory 在 Android 上的支持有限，你可能需要使用其他方法（如使用文件或数据库）来存储加密数据。

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