android實現對文件的加密解密功能（文件保險櫃）

package com.jxd.jxdtest.encryption;

import android.content.Context;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.util.Random;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class MyFileEncryptor {
    private Context mContext = null;
    public MyFileEncryptor(Context context){
        mContext = context;
    }
    @SuppressWarnings("static-access")
    //文件加密的實現方法
    public void encryptFile(String fileName,String encryptedFileName){
        try {
            FileInputStream fis = new FileInputStream(fileName);
            FileOutputStream fos = new FileOutputStream(encryptedFileName);

            //祕鑰自動生成
            KeyGenerator keyGenerator=KeyGenerator.getInstance("AES");
            keyGenerator.init(128);
            Key key=keyGenerator.generateKey();


            byte[] keyValue=key.getEncoded();

            fos.write(keyValue);//記錄輸入的加密密碼的消息摘要

            SecretKeySpec encryKey= new SecretKeySpec(keyValue,"AES");//加密祕鑰

            byte[] ivValue=new byte[16];
            Random random = new Random(System.currentTimeMillis());
            random.nextBytes(ivValue);
            IvParameterSpec iv = new IvParameterSpec(ivValue);//獲取系統時間作爲IV

            fos.write("MyFileEncryptor".getBytes());//文件標識符

            fos.write(ivValue);	//記錄IV
            Cipher cipher = Cipher.getInstance("AES/CFB/PKCS5Padding");
            cipher.init(cipher.ENCRYPT_MODE, encryKey,iv);

            CipherInputStream cis=new CipherInputStream(fis, cipher);

            byte[] buffer=new byte[1024];
            int n=0;
            while((n=cis.read(buffer))!=-1){
                fos.write(buffer,0,n);
            }
            cis.close();
            fos.close();
        } catch (InvalidKeyException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
    @SuppressWarnings("static-access")
    //文件解密的實現代碼
    public void decryptedFile(String encryptedFileName,String decryptedFileName){

        try {
            FileInputStream fis = new FileInputStream(encryptedFileName);
            FileOutputStream fos = new FileOutputStream(decryptedFileName);

            byte[] fileIdentifier=new byte[15];

            byte[] keyValue=new byte[16];
            fis.read(keyValue);//讀記錄的文件加密密碼的消息摘要
            fis.read(fileIdentifier);
            if(new String (fileIdentifier).equals("MyFileEncryptor")){
                SecretKeySpec key= new SecretKeySpec(keyValue,"AES");
                byte[] ivValue= new byte[16];
                fis.read(ivValue);//獲取IV值
                IvParameterSpec iv= new IvParameterSpec(ivValue);
                Cipher cipher = Cipher.getInstance("AES/CFB/PKCS5Padding");
                cipher.init(cipher.DECRYPT_MODE, key,iv);
                CipherInputStream cis= new CipherInputStream(fis, cipher);
                byte[] buffer=new byte[1024];
                int n=0;
                while((n=cis.read(buffer))!=-1){
                    fos.write(buffer,0,n);
                }
                cis.close();
                fos.close();
            }else{
            }
        } catch (InvalidKeyException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }  catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}