MyPhotoEncryptDemo

在android开发过程中有些时候一些重要的图片，我们不希望用户通过文件管理直接能查看，我们该怎么办呢，当然你可以把图片放在android的内部存储中，data/data/下，但毕竟android root用户一大堆，还是解决不了问题。那么我们就需要对图片进行加密，当然加密的方法有很多种，下面给大家推荐我常用的2中方法，基本上可以解决大部分问题。

1、国际标准的AES加密，通过加密流存储文件，查看的时候需要解密，这种方法适合用于非要重要的图片加密。

2、对图片进行处理，在存储文件的时候混入字节，让它查看不了，当我们要查看的时候，我们在读文件的时候在去掉混入的字节就可以了，这种方法适合不是很重要的图片，但是又不希望用户直接在文件管理里能看到。

接下来就是上代码，代码才是最直接的解释：

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package com.test.photoencrypt;  
  
import android.graphics.Bitmap;  
import android.graphics.BitmapFactory;  
import android.os.Bundle;  
import android.os.Environment;  
import android.support.v4.app.FragmentActivity;  
import android.view.View;  
import android.widget.Button;  
import android.widget.ImageView;  
import android.widget.Toast;  
  
import com.test.photoencrypt.utils.FileUtils;  
  
import java.io.ByteArrayOutputStream;  
import java.io.File;  
import java.io.FileInputStream;  
import java.io.FileOutputStream;  
import java.io.IOException;  
import java.io.InputStream;  
  
import javax.crypto.Cipher;  
import javax.crypto.CipherInputStream;  
import javax.crypto.CipherOutputStream;  
import javax.crypto.spec.SecretKeySpec;  
  
/**  
 * Created by fuweiwei on 2015/11/25.  
 */  
public class MainActivity extends FragmentActivity {  
    private Button encryptButton,decryptButton,byteButton,rebyteButton;  
    private ImageView img;  
    private String filePath = Environment.getExternalStorageDirectory().getPath()+ "/test/test.jpg";  
    // AES加密后的文件  
    private static final String outPath = Environment.getExternalStorageDirectory().getPath()+ "/test/encrypt.jpg";  
    // 混入字节加密后文件  
    private static final String bytePath = Environment.getExternalStorageDirectory().getPath()+ "/test/byte.jpg";  
    //AES加密使用的秘钥，注意的是秘钥的长度必须是16位  
    private static final String AES_KEY = "MyDifficultPassw";  
    //混入的字节  
    private static final String BYTE_KEY = "MyByte";  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        encryptButton = (Button) findViewById(R.id.main_encrypt);  
        decryptButton = (Button) findViewById(R.id.main_decrypt);  
        byteButton = (Button) findViewById(R.id.main_addbyte);  
        rebyteButton = (Button) findViewById(R.id.main_removebyte);  
        img = (ImageView) findViewById(R.id.main_img);  
        File file = new File(filePath) ;  
        try {  
            InputStream inputStream = getAssets().open("test.jpg");  
            FileUtils.writeFile(file, inputStream);  
        } catch (IOException e) {  
            e.printStackTrace();  
        }  
  
        encryptButton.setOnClickListener(new View.OnClickListener() {  
            @Override  
            public void onClick(View v) {  
                try {  
                    img.setImageBitmap(null);  
                    aesEncrypt();  
                    Toast.makeText(getApplicationContext(), "加密完成",  
                            Toast.LENGTH_SHORT).show();  
                } catch (Exception e) {  
                    e.printStackTrace();  
                }  
            }  
        });  
  
        decryptButton.setOnClickListener(new View.OnClickListener() {  
            @Override  
            public void onClick(View v) {  
                try {  
                    aesDecrypt();  
                    Toast.makeText(getApplicationContext(), "解密完成",  
                            Toast.LENGTH_SHORT).show();  
                } catch (Exception e) {  
                    e.printStackTrace();  
                }  
            }  
        });  
        byteButton.setOnClickListener(new View.OnClickListener() {  
            @Override  
            public void onClick(View view) {  
                img.setImageBitmap(null);  
                addByte();  
                Toast.makeText(getApplicationContext(), "加密完成",  
                        Toast.LENGTH_SHORT).show();  
            }  
        });  
        rebyteButton.setOnClickListener(new View.OnClickListener() {  
            @Override  
            public void onClick(View view) {  
                removeByte();  
                Toast.makeText(getApplicationContext(), "解密完成",  
                        Toast.LENGTH_SHORT).show();  
            }  
        });  
    }  
  
    /**  
     * 混入字节加密  
     */  
    public  void addByte(){  
        try {  
            //获取图片的字节流  
            Bitmap bitmap = BitmapFactory.decodeFile(filePath);  
            ByteArrayOutputStream baos = new ByteArrayOutputStream();  
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);  
            byte[] bytes = baos.toByteArray();  
            FileOutputStream fops = new FileOutputStream(bytePath);  
            //混入的字节流  
            byte[] bytesAdd = BYTE_KEY.getBytes();  
            fops.write(bytesAdd);  
            fops.write(bytes);  
            fops.flush();  
            fops.close();  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    }  
  
    /**  
     * 移除混入的字节解密图片  
     */  
    public  void removeByte(){  
        try {  
            FileInputStream stream = null;  
            stream = new FileInputStream(new File(bytePath));  
            ByteArrayOutputStream out = new ByteArrayOutputStream(1024);  
            byte[] b = new byte[1024];  
            int n;  
            int i=0;  
            while ((n = stream.read(b)) != -1) {  
                if(i==0){  
                    //第一次写文件流的时候，移除我们之前混入的字节  
                    out.write(b, BYTE_KEY.length(), n-BYTE_KEY.length());  
                }else{  
                    out.write(b, 0, n);  
                }  
                i++;  
            }  
            stream.close();  
            out.close();  
            //获取字节流显示图片  
            byte[] bytes= out.toByteArray();  
            Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);  
            img.setImageBitmap(bitmap);  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    }  
  
    /**  
     * 使用AES加密标准进行加密  
     */  
    public void aesEncrypt()  {  
        try {  
            FileInputStream fis = null;  
            fis = new FileInputStream(filePath);  
            FileOutputStream fos = new FileOutputStream(outPath);  
            //SecretKeySpec此类来根据一个字节数组构造一个 SecretKey  
            SecretKeySpec sks = new SecretKeySpec(AES_KEY.getBytes(),  
                    "AES");  
            //Cipher类为加密和解密提供密码功能,获取实例  
            Cipher cipher = Cipher.getInstance("AES");  
            //初始化  
            cipher.init(Cipher.ENCRYPT_MODE, sks);  
            //CipherOutputStream 为加密输出流  
            CipherOutputStream cos = new CipherOutputStream(fos, cipher);  
            int b;  
            byte[] d = new byte[1024];  
            while ((b = fis.read(d)) != -1) {  
                cos.write(d, 0, b);  
            }  
            cos.flush();  
            cos.close();  
            fis.close();  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
  
    }  
  
    /**  
     * 使用AES标准解密  
     */  
    public void aesDecrypt() {  
        try {  
            FileInputStream fis = null;  
            fis = new FileInputStream(outPath);  
            ByteArrayOutputStream out = new ByteArrayOutputStream(1024);  
            SecretKeySpec sks = new SecretKeySpec(AES_KEY.getBytes(),  
                    "AES");  
            Cipher cipher = Cipher.getInstance("AES");  
            cipher.init(Cipher.DECRYPT_MODE, sks);  
            //CipherInputStream 为加密输入流  
            CipherInputStream cis = new CipherInputStream(fis, cipher);  
            int b;  
            byte[] d = new byte[1024];  
            while ((b = cis.read(d)) != -1) {  
                out.write(d, 0, b);  
            }  
            out.flush();  
            out.close();  
            cis.close();  
            //获取字节流显示图片  
            byte[] bytes= out.toByteArray();  
            Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);  
            img.setImageBitmap(bitmap);  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
  
    }  
  
}