Android开发数据加密之手机端的加密解密

Android应用程序在与服务器进行交互的时候，有时需要对传输的数据进行加密处理，以保证传输数据的安全。如果数据量不大的话，可以采用3De加密，在服务器端采用对应的密钥进行解密即可，同理，服务器端进行加密的数据，在手机端也可以进行解密处理，其中在手机端需要三个文件来演示这个功能：Base64.java，Des3.java,TestDes.java;

Base64.java

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.OutputStream;

/**

 * Base64编码工具类

 * 

 * @author  

 * @date 2012-10-11

 */

public class Base64 {
private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();

public static String encode(byte[] data) {
int start = 0;
int len = data.length;
StringBuffer buf = new StringBuffer(data.length * 3 / 2);

int end = len - 3;
int i = start;
int n = 0;

while (i <= end) {
int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 0x0ff) << 8) | (((int) data[i + 2]) & 0x0ff);

buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append(legalChars[(d >> 6) & 63]);
buf.append(legalChars[d & 63]);

i += 3;

if (n++ >= 14) {
n = 0;
buf.append(" ");
}
}

if (i == start + len - 2) {
int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 255) << 8);

buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append(legalChars[(d >> 6) & 63]);
buf.append("=");
} else if (i == start + len - 1) {
int d = (((int) data[i]) & 0x0ff) << 16;

buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append("==");
}

return buf.toString();
}

private static int decode(char c) {
if (c >= 'A' && c <= 'Z')
return ((int) c) - 65;
else if (c >= 'a' && c <= 'z')
return ((int) c) - 97 + 26;
else if (c >= '0' && c <= '9')
return ((int) c) - 48 + 26 + 26;
else
switch (c) {
case '+':
return 62;
case '/':
return 63;
case '=':
return 0;
default:
throw new RuntimeException("unexpected code: " + c);
}
}

/**
* Decodes the given Base64 encoded String to a new byte array. The byte array holding the decoded data is returned.
*/

public static byte[] decode(String s) {

ByteArrayOutputStream bos = new ByteArrayOutputStream();
try {
decode(s, bos);
} catch (IOException e) {
throw new RuntimeException();
}
byte[] decodedBytes = bos.toByteArray();
try {
bos.close();
bos = null;
} catch (IOException ex) {
System.err.println("Error while decoding BASE64: " + ex.toString());
}
return decodedBytes;
}

private static void decode(String s, OutputStream os) throws IOException {
int i = 0;

int len = s.length();

while (true) {
while (i < len && s.charAt(i) <= ' ')
i++;

if (i == len)
break;

int tri = (decode(s.charAt(i)) << 18) + (decode(s.charAt(i + 1)) << 12) + (decode(s.charAt(i + 2)) << 6) + (decode(s.charAt(i + 3)));

os.write((tri >> 16) & 255);
if (s.charAt(i + 2) == '=')
break;
os.write((tri >> 8) & 255);
if (s.charAt(i + 3) == '=')
break;
os.write(tri & 255);

i += 4;
}
}

}

Des3.java

import java.security.Key;

import javax.crypto.Cipher;

import javax.crypto.SecretKeyFactory;

import javax.crypto.spec.DESedeKeySpec;

import javax.crypto.spec.IvParameterSpec;

/**

 * 3DES加密工具类

 * 

 * @author 

 * @date 2013-03-11

 */

public class Des3 {
// 密钥
private final static String secretKey = "zyhzyhzyhzyhzyhzyhzyhzyh";
// 向量
private final static String iv = "01234567";
// 加解密统一使用的编码方式
private final static String encoding = "utf-8";

/**
* 3DES加密
* 
* @param plainText 普通文本
* @return
* @throws Exception 
*/
public static String encode(String plainText) throws Exception {
Key deskey = null;
DESedeKeySpec spec = new DESedeKeySpec(secretKey.getBytes(),0); //Uses the first 24 bytes in key, beginning at offset inclusive, as the DES-EDE key.
SecretKeyFactory keyfactory = SecretKeyFactory.getInstance("desede");
deskey = keyfactory.generateSecret(spec);

Cipher cipher = Cipher.getInstance("desede/CBC/PKCS5Padding");
IvParameterSpec ips = new IvParameterSpec(iv.getBytes());
cipher.init(Cipher.ENCRYPT_MODE, deskey, ips);
byte[] encryptData = cipher.doFinal(plainText.getBytes(encoding));
return Base64.encode(encryptData);
}

/**
* 3DES解密
* 
* @param encryptText 加密文本
* @return
* @throws Exception
*/
public static String decode(String encryptText) throws Exception {
Key deskey = null;
DESedeKeySpec spec = new DESedeKeySpec(secretKey.getBytes(),0);
SecretKeyFactory keyfactory = SecretKeyFactory.getInstance("desede");
deskey = keyfactory.generateSecret(spec);
Cipher cipher = Cipher.getInstance("desede/CBC/PKCS5Padding");
IvParameterSpec ips = new IvParameterSpec(iv.getBytes());
cipher.init(Cipher.DECRYPT_MODE, deskey, ips);

byte[] decryptData = cipher.doFinal(Base64.decode(encryptText));

return new String(decryptData, encoding);
}

}

TestDes.java

public class TestDes {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
String planText = "zyh0";
//Des3 d = new Des3();
String strEncode = "";
String strDecode = "";
System.out.println("加密前："+planText);
try {
strEncode = Des3.encode(planText);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("加密后："+strEncode);
try{
strDecode = Des3.decode(strEncode);
}catch(Exception e)
{
e.printStackTrace();
}
System.out.println("解密后："+strDecode);
}

}