Android中如何加密和解密文件

Android中的文件加密和解密是一项重要的安全功能，它可以帮助我们保护敏感数据免受未经授权的访问。在本文中，我们将介绍如何在Android应用程序中 ，并提供一些案例代码来演示文件加密和解密的实现方式。

java
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.security.spec.KeySpec;
public class FileEncryptionUtils {
    private static final String ALGORITHM = "AES";
    private static final String TRANSFORMATION = "AES/CBC/PKCS5Padding";
    private static final String SECRET_KEY = "my_secret_key";
    private static final String SALT = "my_salt";
    public static void encryptFile(File inputFile, File outputFile) throws Exception {
        FileInputStream fis = new FileInputStream(inputFile);
        FileOutputStream fos = new FileOutputStream(outputFile);
        SecretKey secretKey = generateSecretKey();
        Cipher cipher = Cipher.getInstance(TRANSFORMATION);
        cipher.init(Cipher.ENCRYPT_MODE, secretKey, new IvParameterSpec(new byte[cipher.getBlockSize()]));
        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = fis.read(buffer)) != -1) {
            byte[] encryptedBytes = cipher.update(buffer, 0, bytesRead);
            fos.write(encryptedBytes);
        }
        byte[] encryptedBytes = cipher.doFinal();
        fos.write(encryptedBytes);
        fis.close();
        fos.close();
    }
    private static SecretKey generateSecretKey() throws Exception {
        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        KeySpec spec = new PBEKeySpec(SECRET_KEY.toCharArray(), SALT.getBytes(), 65536, 256);
        SecretKey tmp = factory.generateSecret(spec);
        return new SecretKeySpec(tmp.getEncoded(), ALGORITHM);
    }
}

java
public class FileDecryptionUtils {
    private static final String ALGORITHM = "AES";
    private static final String TRANSFORMATION = "AES/CBC/PKCS5Padding";
    private static final String SECRET_KEY = "my_secret_key";
    private static final String SALT = "my_salt";
    public static void decryptFile(File inputFile, File outputFile) throws Exception {
        FileInputStream fis = new FileInputStream(inputFile);
        FileOutputStream fos = new FileOutputStream(outputFile);
        SecretKey secretKey = generateSecretKey();
        Cipher cipher = Cipher.getInstance(TRANSFORMATION);
        cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(new byte[cipher.getBlockSize()]));
        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = fis.read(buffer)) != -1) {
            byte[] decryptedBytes = cipher.update(buffer, 0, bytesRead);
            fos.write(decryptedBytes);
        }
        byte[] decryptedBytes = cipher.doFinal();
        fos.write(decryptedBytes);
        fis.close();
        fos.close();
    }
    private static SecretKey generateSecretKey() throws Exception {
        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        KeySpec spec = new PBEKeySpec(SECRET_KEY.toCharArray(), SALT.getBytes(), 65536, 256);
        SecretKey tmp = factory.generateSecret(spec);
        return new SecretKeySpec(tmp.getEncoded(), ALGORITHM);
    }
}