I tried to do encrypted part by myself, it doesn't work. :( I attached it
for you to look at.
On Sunday, May 29, 2016 at 10:40:49 AM UTC-4, hezaveh wrote:
>
> Hi,
>
> I want an android app, one EditText to enter input. and then a button, by
> clicking the button it calls encrypt method and then a textview shows the
> encrypted message. The other button to decrypt the message, calls decrypt
> method. last textview shows the dencrypted message which is same as the
> input.
>
> Here is a link that implement RSA encryption (
> https://sites.google.com/site/mobilesecuritylabware/3-data-location-privacy/lab-activity/cryptography/cryptography-mobile-labs/encryption-decryption/2-lab-activity/lab2-rsa-encryption-program-android-studio).
>
> I want exactly same for goldwasser micali.
>
> Thanks
>
> On Saturday, May 28, 2016 at 7:34:01 PM UTC-4, TreKing wrote:
>>
>>
>> On Fri, May 27, 2016 at 4:17 PM, hezaveh <mari.h...@gmail.com> wrote:
>>
>>> I have a java code of goldwasser-micali encryption (attached), and I
>>> need your help to implement it in android studio. can anybody help me?
>>>
>>
>> Java code is not something you "implement" in Android Studio. What are
>> you actually trying to achieve?
>>
>>
>> -------------------------------------------------------------------------------------------------
>> TreKing <http://sites.google.com/site/rezmobileapps/treking> - Chicago
>> transit tracking app for Android-powered devices
>>
>
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package com.example.goldwasser_micali;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import java.math.BigInteger;
import java.security.SecureRandom;
public class MainActivity extends AppCompatActivity {
/**
* SYSTEM PARAMETERS
*/
//Bitsize
private int bitSize;
/**
* KEYS
*/
//Private key
private BigInteger p, q;
//Public key
private BigInteger x, n;
//Random number generator
public SecureRandom rand;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final Button enButton = (Button) findViewById(R.id.enbutton);
final Button deButton = (Button) findViewById(R.id.debutton);
final EditText input = (EditText) findViewById(R.id.Input);
final EditText Raw = (EditText) findViewById(R.id.raw);
final EditText output = (EditText) findViewById(R.id.OriginText);
enButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String j = input.toString();
MainActivity gm = new MainActivity(512);
for (int i = 0; i < j.length(); i++) {
BigInteger c = gm.encrypt(j.charAt(i) == '1');
Raw.setText(c.toString());
}
}
});
}
/**
* Constructor generating key parameters
*
* @param bitSize: size in bits of p and q, this number must be a power of 2, for 1024 security bitSize must be 512.
*/
public MainActivity(int bitSize) {
this.bitSize = bitSize;
this.rand = new SecureRandom();
generateKeys();
}
/**
* Key parameters of Benaloh's cryptosystem
*/
public void generateKeys() {
BigInteger one = BigInteger.ONE, two = new BigInteger("2");
p = randomNumber(true, bitSize);
do {
q = randomNumber(true, bitSize);
} while (p.equals(q));
n = p.multiply(q);
do {
x = randomNumber(false, bitSize * 2);
}
while (x.compareTo(n) >= 0 || x.modPow(p.subtract(one).divide(two), p).equals(one) || x.modPow(q.subtract(one).divide(two), q).equals(one));
}
/**
* BigInteger random number generator
*
* @param prime true if the number must be prime, false otherwise
* @param size: size in bits
* @return random number with the criteria selected.
*/
private BigInteger randomNumber(boolean prime, int size) {
if (prime)
return BigInteger.probablePrime(size, rand);
BigInteger number = null;
byte bNumber[] = new byte[(int) Math.ceil(size / 8.0)];
do {
rand.nextBytes(bNumber);
number = new BigInteger(bNumber);
} while (number.compareTo(BigInteger.ZERO) <= 0);
return number;
}
public BigInteger encrypt(boolean bit) {
BigInteger y;
do {
y = randomNumber(false, bitSize * 2);
} while (y.compareTo(n) >= 0);
return y.modPow(new BigInteger("2"), n).multiply(bit ? x : BigInteger.ONE).remainder(n);
}
public boolean decrypt(BigInteger c) {
boolean qr;
qr = c.modPow(p.subtract(BigInteger.ONE).divide(new BigInteger("2")), p).equals(BigInteger.ONE);
qr &= c.modPow(q.subtract(BigInteger.ONE).divide(new BigInteger("2")), q).equals(BigInteger.ONE);
return qr;
}
/** public static void main(String[] args) {
String m = "101011101000011011111000000110101";
MainActivity gm = new MainActivity(512);
System.out.println(m);
for (int i = 0; i < m.length(); i++) {
BigInteger c = gm.encrypt(m.charAt(i) == '1');
System.out.print((gm.decrypt(c) ? 0 : 1));}
} **/
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
