android aes加密解密文件

好的，这里是一个简单的示例，展示了如何在 Android 中使用 AES 加密和解密文件：

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.security.MessageDigest;
import java.util.Arrays;

public class AesUtil {

    private static final String ALGORITHM = "AES/CBC/PKCS5Padding";
    private static final String SECRET_KEY = "my_secret_key";
    private static final String IV = "my_initialization_vector";

    public static void encrypt(String inputFile, String outputFile) throws Exception {
        SecretKeySpec secretKeySpec = generateKey(SECRET_KEY);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(IV.getBytes("UTF-8"));

        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);

        FileInputStream inputStream = new FileInputStream(inputFile);
        FileOutputStream outputStream = new FileOutputStream(outputFile);

        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            byte[] output = cipher.update(buffer, 0, bytesRead);
            if (output != null) {
                outputStream.write(output);
            }
        }
        byte[] output = cipher.doFinal();
        if (output != null) {
            outputStream.write(output);
        }

        inputStream.close();
        outputStream.close();
    }

    public static void decrypt(String inputFile, String outputFile) throws Exception {
        SecretKeySpec secretKeySpec = generateKey(SECRET_KEY);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(IV.getBytes("UTF-8"));

        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);

        FileInputStream inputStream = new FileInputStream(inputFile);
        FileOutputStream outputStream = new FileOutputStream(outputFile);

        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            byte[] output = cipher.update(buffer, 0, bytesRead);
            if (output != null) {
                outputStream.write(output);
            }
        }
        byte[] output = cipher.doFinal();
        if (output != null) {
            outputStream.write(output);
        }

        inputStream.close();
        outputStream.close();
    }

    private static SecretKeySpec generateKey(String key) throws Exception {
        byte[] keyBytes = key.getBytes("UTF-8");
        MessageDigest sha = MessageDigest.getInstance("SHA-256");
        keyBytes = sha.digest(keyBytes);
        keyBytes = Arrays.copyOf(keyBytes, 16);
        return new SecretKeySpec(keyBytes, "AES");
    }
}

在此示例中，我们使用 AES/CBC/PKCS5Padding 加密模式和 SHA-256 哈希算法生成密钥。我们将密钥和初始向量 IV 保存为常量，但您可以根据需要进行更改。

要使用此示例，请在您的代码中调用 `AesUtil.encrypt(inputFile, outputFile)` 或 `AesUtil.decrypt(inputFile, outputFile)` 方法，其中 `inputFile` 是要加密或解密的文件路径，而 `outputFile` 是加密或解密后的文件路径。

请注意，此示例中的加密和解密操作是阻塞的，并且使用了相对较小的缓冲区。对于大文件和需要异步处理的情况，您需要进行适当的优化。