android Java语言非对称加密的实现

package com.example.encryption;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;

import javax.crypto.Cipher;

import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class EntryptionActivity extends Activity {

private static final String TAG="EntryptionActivity";
private PrivateKey privateKey;
private String inputString;
private EditText encryptionEditText;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_entryption);
encryptionEditText = (EditText)findViewById(R.id.encryptionedit);
encryptionEditText.clearFocus();
//((InputMethodManager)getSystemService(INPUT_METHOD_SERVICE)).showSoftInput(encryptionEditText,R.id.encryptionedit);
Button decrypitionButton = (Button)findViewById(R.id.decryptionbutton);
Button encrypiontButton = (Button)findViewById(R.id.encryptionbutton);
encrypiontButton.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {
try {
inputString = encryptionEditText.getText().toString();
PublicEnrypt(inputString);
} catch (Exception e) {
e.printStackTrace();
}
}
});

decrypitionButton.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {
try {
privateDecrypt();
} catch (Exception e) {
e.printStackTrace();
}
}
});

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_entryption, menu);
return true;
}

/*
* 公钥加密
*/
private void PublicEnrypt(String inputString)throws Exception {

Log.i(TAG, "----------------->加密");
Cipher cipher =Cipher.getInstance("RSA");
//实例化Key
KeyPairGenerator keyPairGenerator=KeyPairGenerator.getInstance("RSA");
//设置密钥长度,自己加入
keyPairGenerator.initialize(1024);
//获取一对钥匙
KeyPair keyPair=keyPairGenerator.generateKeyPair();
//获得公钥
Key publicKey=keyPair.getPublic();
//获得私钥
privateKey=keyPair.getPrivate();
//用公钥加密
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
byte [] result=cipher.doFinal(inputString.getBytes("UTF-8"));
saveData(result,"public_encryt.dat");
//将Key写入到文件
//saveKey(privateKey,"zxx_private.key");
//加密后的数据写入到文件

}

/*
* 私钥解密
*/
private void privateDecrypt() throws Exception {

Cipher cipher=Cipher.getInstance("RSA");
//得到Key
//Key privateKey=readKey("zxx_private.key");
//Log.i(TAG, "私钥："+ privateKey.toString());
//用私钥去解密
//cipher.init(Cipher.DECRYPT_MODE, privateKey);
cipher.init(Cipher.DECRYPT_MODE, privateKey);
//读数据源
byte [] src =readData("public_encryt.dat");
Log.i(TAG, "----------------->解密");
//得到解密后的结果
byte[] result=cipher.doFinal(src);
//二进制数据要变成字符串需解码
//System.out.println(new String(result,"UTF-8"));
String outputString = new String(result, "UTF-8");
Log.i(TAG, outputString);
Toast.makeText(getApplicationContext(), "您输入的明文是：" + outputString,
Toast.LENGTH_LONG).show();

}

/**
* 存储加密后的数据
* @param result 加密数据
* @param fileName 存储文件名
* @throws Exception
*/
private void saveData(byte[] result, String fileName) throws Exception {
FileOutputStream fosData = openFileOutput(fileName, MODE_PRIVATE);
fosData.write(result);
fosData.close();
}

public static void saveKey(Key key,String fileName)throws Exception{
FileOutputStream fosKey=new FileOutputStream(fileName);
ObjectOutputStream oosSecretKey =new ObjectOutputStream(fosKey);
oosSecretKey.writeObject(key);
oosSecretKey.close();
fosKey.close();
}

/*//将私钥存储，可以减少内存的占用，但存储和读取降低了程序的执行效率。
private static Key readKey(String fileName) throws Exception {

FileInputStream fisKey=new FileInputStream(fileName);
ObjectInputStream oisKey =new ObjectInputStream(fisKey);
Key key=(Key)oisKey.readObject();
Log.i(TAG, "私钥" + key.toString());
oisKey.close();
fisKey.close();
Log.i(TAG, "-----------读取密钥");
return key;
}*/

private  byte[] readData(String filename) throws Exception {
FileInputStream fisDat=openFileInput(filename);
byte [] src=new byte [fisDat.available()];
int len =fisDat.read(src);
int total =0;
while(total<src.length){
total +=len;
len=fisDat.read(src,total,src.length-total);
}
fisDat.close();
return src;
}

}