6mKYqEy1

1package android.encdecsms;
2import java.security.Key;
3import java.util.ArrayList;
4import javax.crypto.Cipher;
5import javax.crypto.spec.SecretKeySpec;
6import android.app.Activity;
7import android.os.Bundle;
8import android.telephony.SmsManager;
9import android.view.View;
10import android.widget.Button;
11import android.widget.EditText;
12import android.widget.Toast;
13public class EncDecSMSActivity extends Activity {
14 /** Called when the activity is first created. */
15 EditText recNum;
16 EditText secretKey;
17 EditText msgContent;
18 Button send;
19 Button cancel;
20 @Override
21 public void onCreate(Bundle savedInstanceState) {
22  super.onCreate(savedInstanceState);
23  setContentView(R.layout.main);
24  recNum = (EditText) findViewById(R.id.recNum);
25  secretKey = (EditText) findViewById(R.id.secretKey);
26  msgContent = (EditText) findViewById(R.id.msgContent);
27  send = (Button) findViewById(R.id.Send);
28  cancel = (Button) findViewById(R.id.cancel);
29  // finish the activity when click Cancel button
30  cancel.setOnClickListener(new View.OnClickListener() {
31   public void onClick(View v) {
32    finish();
33   }
34  });
35  Fall 2017 44
36  // encrypt the message and send when click Send button
37  send.setOnClickListener(new View.OnClickListener() {
38   public void onClick(View v) {
39    String recNumString = recNum.getText().toString();
40    String secretKeyString = secretKey.getText().toString();
41    String msgContentString = msgContent.getText().toString();
42    // check for the validity of the user input
43    // key length should be 16 characters as defined by AES-128-bit
44    if (recNumString.length() > 0 && secretKeyString.length() > 0 && msgContentString.length() > 0 && secretKeyString.length() == 16) {
45     // encrypt the message
46     byte[] encryptedMsg = encryptSMS(secretKeyString,
47      msgContentString);
48     // convert the byte array to hex format in order for
49     // transmission
50     String msgString = byte2hex(encryptedMsg);
51     // send the message through SMS
52     sendSMS(recNumString, msgString);
53     // finish
54     finish();
55    } else
56     Toast.makeText(
57      getBaseContext(),
58      "Please enter phone number, secret key and the message. Secret key must be 16 characters!",
59      Toast.LENGTH_SHORT).show();
60   }
61  });
62 }
63 public static void sendSMS(String recNumString, String encryptedMsg) {
64   try {
65    // get a SmsManager
66    SmsManager smsManager = SmsManager.getDefault();
67    // Message may exceed 160 characters
68    // need to divide the message into multiples
69    ArrayList < String > parts = smsManager.divideMessage(encryptedMsg);
70    smsManager.sendMultipartTextMessage(recNumString, null, parts,
71     null, null);
72   } catch (Exception e) {
73    e.printStackTrace();
74   }
75  }
76  // utility function
77 public static String byte2hex(byte[] b) {
78   String hs = "";
79   String stmp = "";
80   Fall 2017 45
81   for (int n = 0; n < b.length; n++) {
82    stmp = Integer.toHexString(b[n] & 0xFF);
83    if (stmp.length() == 1)
84     hs += ("0" + stmp);
85    else
86     hs += stmp;
87   }
88   return hs.toUpperCase();
89  }
90  // encryption function
91 public static byte[] encryptSMS(String secretKeyString,
92  String msgContentString) {
93  try {
94   byte[] returnArray;
95   // generate AES secret key from user input
96   Key key = generateKey(secretKeyString);
97   // specify the cipher algorithm using AES
98   Cipher c = Cipher.getInstance("AES");
99   // specify the encryption mode
100   c.init(Cipher.ENCRYPT_MODE, key);
101   // encrypt
102   returnArray = c.doFinal(msgContentString.getBytes());
103   return returnArray;
104  } catch (Exception e) {
105   e.printStackTrace();
106   byte[] returnArray = null;
107   return returnArray;
108  }
109 }
110 private static Key generateKey(String secretKeyString) throws Exception {
111  // generate secret key from string
112  Key key = new SecretKeySpec(secretKeyString.getBytes(), "AES");
113  return key;
114 }
115}