用MD5处理明文密码加密

很多的网络相关的软件都需要用户名密码登录，在开发的时候像这些密码都是保存在SharedPreferences中，这些密码保存在/data/data/包名/shared_prefs下，保存在一个XML文件中，如下：

可以用FileBrower查看

开始说道正题，MD5加密算法虽然现在有些人已经将其解开了，但是它的加密机制依然很强大，我想绝大对数还是不会解开的。MD5加密算法是单向加密，只能用你的密码才能解开，要不就是会解密算法，否则想都别想解开。为了防止这种情况的发生。还可以对加密过的密码进行再次加密。

下面是个小例子：

main.xml

Xml代码

1. <?xml version="1.0" encoding="utf-8"?>
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
3. android:orientation="vertical"
4. android:layout_;fill_parent"
5. android:layout_height="fill_parent"
6. >
7. <EditText
8. android:id="@+id/username"
9. android:layout_;fill_parent"
10. android:layout_height="wrap_content"
11. android:layout_marginLeft="10dp"
12. android:layout_marginTop="20dp"
13. android:layout_marginRight="10dp"
14. android:hint="帐号"
15. />
16. <EditText
17. android:id="@+id/password"
18. android:password="true"
19. android:layout_;fill_parent"
20. android:layout_height="wrap_content"
21. android:layout_marginLeft="10dp"
22. android:layout_marginTop="10dp"
23. android:layout_marginRight="10dp"
24. android:hint="密码"
25. />
26. <Button
27. android:id="@+id/save"
28. android:text="保存"
29. android:layout_;fill_parent"
30. android:layout_height="wrap_content"
31. android:layout_marginLeft="10dp"
32. android:layout_marginTop="10dp"
33. android:layout_marginRight="10dp"
34. />
35. <Button
36. android:id="@+id/login"
37. android:layout_;fill_parent"
38. android:layout_height="wrap_content"
39. android:layout_marginLeft="10dp"
40. android:layout_marginTop="10dp"
41. android:layout_marginRight="10dp"
42. android:text="登录"
43. />
44. </LinearLayout>

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_;fill_parent" android:layout_height="fill_parent" > <EditText android:id="@+id/username" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginLeft="10dp" android:layout_marginTop="20dp" android:layout_marginRight="10dp" android:hint="帐号" /> <EditText android:id="@+id/password" android:password="true" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginLeft="10dp" android:layout_marginTop="10dp" android:layout_marginRight="10dp" android:hint="密码" /> <Button android:id="@+id/save" android:text="保存" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginLeft="10dp" android:layout_marginTop="10dp" android:layout_marginRight="10dp" /> <Button android:id="@+id/login" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginLeft="10dp" android:layout_marginTop="10dp" android:layout_marginRight="10dp" android:text="登录" /> </LinearLayout>

login.xml

Xml代码

1. <?xml version="1.0" encoding="utf-8"?>
2. <LinearLayout
3. xmlns:android="http://schemas.android.com/apk/res/android"
4. android:layout_;match_parent"
5. android:layout_height="match_parent"
6. android:orientation="vertical">
7. <TextView
8. android:layout_;fill_parent"
9. android:layout_height="wrap_content"
10. android:text="login successful!"
11. />
12. </LinearLayout>

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_;match_parent" android:layout_height="match_parent" android:orientation="vertical"> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="login successful!" /> </LinearLayout>

login.java

Java代码

1. package com.loulijun.md5demo;    
3. import android.app.Activity;    
4. import android.os.Bundle;    
6. public class Login extends Activity {    
8. @Override
9. protected void onCreate(Bundle savedInstanceState) {    
10. // TODO Auto-generated method stub  
11. super.onCreate(savedInstanceState);    
12.         setContentView(R.layout.login);    
13.     }    
15. }  

package com.loulijun.md5demo; import android.app.Activity; import android.os.Bundle; public class Login extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(R.layout.login); } }

MD5Demo.java

Java代码

1. package com.loulijun.md5demo;    
3. import java.security.MessageDigest;    
5. import android.app.Activity;    
6. import android.content.Intent;    
7. import android.content.SharedPreferences;    
8. import android.os.Bundle;    
9. import android.view.View;    
10. import android.widget.Button;    
11. import android.widget.EditText;    
12. import android.widget.Toast;    
14. public class MD5Demo extends Activity {    
15. private EditText username,password;    
16. private Button savebtn,loginbtn;    
17.     String user,pass;    
18. @Override
19. public void onCreate(Bundle savedInstanceState) {    
20. super.onCreate(savedInstanceState);    
21.         setContentView(R.layout.main);    
22.         username = (EditText)findViewById(R.id.username);    
23.         password = (EditText)findViewById(R.id.password);    
24.         savebtn = (Button)findViewById(R.id.save);    
25.         loginbtn = (Button)findViewById(R.id.login);    
27.         savebtn.setOnClickListener(new Button.OnClickListener()    
28.         {    
30. @Override
31. public void onClick(View v) {    
32.                 SharedPreferences pre = getSharedPreferences("loginvalue",MODE_WORLD_WRITEABLE);    
33.                 pass = MD5(password.getText().toString());    
34.                 user = username.getText().toString();    
35. if(!pass.equals("")&&!user.equals(""))    
36.                 {    
37.                       pre.edit().putString("username", username.getText().toString()).    
38.                       putString("password",encryptmd5(pass)).commit();    
39.                       Toast.makeText(getApplicationContext(), "保存成功!", Toast.LENGTH_SHORT).show();    
40.                 }else
41.                 {    
42.                     Toast.makeText(getApplicationContext(), "密码不能为空！", Toast.LENGTH_LONG).show();    
43.                 }    
46.             }    
48.         });    
49.         loginbtn.setOnClickListener(new Button.OnClickListener()    
50.         {    
53. @Override
54. public void onClick(View v) {    
55.                 SharedPreferences sp = getSharedPreferences("loginvalue", MODE_WORLD_READABLE);    
56.                 String loginuser = sp.getString("username", null);    
57.                 String loginpass = sp.getString("password", null);    
59.                 user = username.getText().toString();    
60.                 pass = password.getText().toString();    
62.                 String passmd5 = MD5(pass);    
63.                 String encryptmd5 = encryptmd5(passmd5);    
65.                 System.out.println("username="+loginuser+"-------------password="+loginpass);    
66.                   System.out.println("user=="+user+"-------------encryptmd5=="+encryptmd5);    
67. if(!user.equals("")&&!pass.equals(""))    
68.                   {    
69. if( user.equals(loginuser)&& encryptmd5.equals(loginpass))    
70.                       {    
71.                           Intent intent = new Intent();    
72.                           intent.setClass(MD5Demo.this, Login.class);    
73.                           MD5Demo.this.startActivity(intent);      
74.                           finish();    
75.                       }else
76.                       {                   
77.                           Toast.makeText(getApplicationContext(), "密码是错误的！", Toast.LENGTH_LONG).show();    
78.                       }    
79.                   }else
80.                   {    
81.                       Toast.makeText(getApplicationContext(), "密码不能为空！", Toast.LENGTH_LONG).show();    
82.                   }    
84.             }    
86.         });    
87.     }    
89. //MD5加密，32位  
90. public static String MD5(String str)    
91.     {    
92.         MessageDigest md5 = null;    
93. try
94.         {    
95.             md5 = MessageDigest.getInstance("MD5");    
96.         }catch(Exception e)    
97.         {    
98.             e.printStackTrace();    
99. return "";    
100.         }    
102. char[] charArray = str.toCharArray();    
103. byte[] byteArray = new byte[charArray.length];    
105. for(int i = 0; i &lt; charArray.length; i++)    
106.         {    
107.             byteArray[i] = (byte)charArray[i];    
108.         }    
109. byte[] md5Bytes = md5.digest(byteArray);    
111.         StringBuffer hexValue = new StringBuffer();    
112. for( int i = 0; i &lt; md5Bytes.length; i++)    
113.         {    
114. int val = ((int)md5Bytes[i])&0xff;    
115. if(val &lt; 16)    
116.             {    
117.                 hexValue.append("0");    
118.             }    
119.             hexValue.append(Integer.toHexString(val));    
120.         }    
121. return hexValue.toString();    
122.     }    
124. // 可逆的加密算法  
125. public static String encryptmd5(String str) {    
126. char[] a = str.toCharArray();    
127. for (int i = 0; i &lt; a.length; i++)     
128.         {    
129.                 a[i] = (char) (a[i] ^ 'l');    
130.         }    
131.         String s = new String(a);    
132. return s;    
133.     }    
135. }   

package com.loulijun.md5demo; import java.security.MessageDigest; import android.app.Activity; import android.content.Intent; import android.content.SharedPreferences; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.Toast; public class MD5Demo extends Activity { private EditText username,password; private Button savebtn,loginbtn; String user,pass; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); username = (EditText)findViewById(R.id.username); password = (EditText)findViewById(R.id.password); savebtn = (Button)findViewById(R.id.save); loginbtn = (Button)findViewById(R.id.login); savebtn.setOnClickListener(new Button.OnClickListener() { @Override public void onClick(View v) { SharedPreferences pre = getSharedPreferences("loginvalue",MODE_WORLD_WRITEABLE); pass = MD5(password.getText().toString()); user = username.getText().toString(); if(!pass.equals("")&&!user.equals("")) { pre.edit().putString("username", username.getText().toString()). putString("password",encryptmd5(pass)).commit(); Toast.makeText(getApplicationContext(), "保存成功!", Toast.LENGTH_SHORT).show(); }else { Toast.makeText(getApplicationContext(), "密码不能为空！", Toast.LENGTH_LONG).show(); } } }); loginbtn.setOnClickListener(new Button.OnClickListener() { @Override public void onClick(View v) { SharedPreferences sp = getSharedPreferences("loginvalue", MODE_WORLD_READABLE); String loginuser = sp.getString("username", null); String loginpass = sp.getString("password", null); user = username.getText().toString(); pass = password.getText().toString(); String passmd5 = MD5(pass); String encryptmd5 = encryptmd5(passmd5); System.out.println("username="+loginuser+"-------------password="+loginpass); System.out.println("user=="+user+"-------------encryptmd5=="+encryptmd5); if(!user.equals("")&&!pass.equals("")) { if( user.equals(loginuser)&& encryptmd5.equals(loginpass)) { Intent intent = new Intent(); intent.setClass(MD5Demo.this, Login.class); MD5Demo.this.startActivity(intent); finish(); }else { Toast.makeText(getApplicationContext(), "密码是错误的！", Toast.LENGTH_LONG).show(); } }else { Toast.makeText(getApplicationContext(), "密码不能为空！", Toast.LENGTH_LONG).show(); } } }); } //MD5加密，32位 public static String MD5(String str) { MessageDigest md5 = null; try { md5 = MessageDigest.getInstance("MD5"); }catch(Exception e) { e.printStackTrace(); return ""; } char[] charArray = str.toCharArray(); byte[] byteArray = new byte[charArray.length]; for(int i = 0; i &lt; charArray.length; i++) { byteArray[i] = (byte)charArray[i]; } byte[] md5Bytes = md5.digest(byteArray); StringBuffer hexValue = new StringBuffer(); for( int i = 0; i &lt; md5Bytes.length; i++) { int val = ((int)md5Bytes[i])&0xff; if(val &lt; 16) { hexValue.append("0"); } hexValue.append(Integer.toHexString(val)); } return hexValue.toString(); } // 可逆的加密算法 public static String encryptmd5(String str) { char[] a = str.toCharArray(); for (int i = 0; i &lt; a.length; i++) { a[i] = (char) (a[i] ^ 'l'); } String s = new String(a); return s; } }

程序很简单，下面是运行的效果：