非對(duì)稱型加密非常適合多個(gè)客戶端和服務(wù)器之間的秘密通訊，客戶端使用同一個(gè)公鑰將明文加密，而這個(gè)公鑰不能逆向的解密，密文發(fā)送到服務(wù)器后有服務(wù)器端用私鑰解密，這樣就做到了明文的加密傳送。
非對(duì)稱型加密也有它先天的缺點(diǎn)，加密、解密速度慢制約了它的發(fā)揮，如果你有大量的文字需要加密傳送，建議你通過(guò)非對(duì)稱型加密來(lái)把對(duì)稱型‘密鑰’分發(fā)到客戶端，及時(shí)更新對(duì)稱型‘密鑰’。
package com.paul.module.common.util;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import javax.crypto.Cipher;
public class RSASecurityUtil2 {
/** 指定加密算法為RSA */
private static final String ALGORITHM = "RSA";
/** 密鑰長(zhǎng)度，用來(lái)初始化 */
private static final int KEYSIZE = 1024;
/** 指定公鑰存放文件 */
private static String PUBLIC_KEY_FILE = "PublicKey";
/** 指定私鑰存放文件 */
private static String PRIVATE_KEY_FILE = "PrivateKey";
/**
* 生成密鑰對(duì)
* @throws Exception
*/
private static void generateKeyPair() throws Exception {
// /** RSA算法要求有一個(gè)可信任的隨機(jī)數(shù)源 */
// SecureRandom secureRandom = new SecureRandom();
/** 為RSA算法創(chuàng)建一個(gè)KeyPairGenerator對(duì)象 */
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);
/** 利用上面的隨機(jī)數(shù)據(jù)源初始化這個(gè)KeyPairGenerator對(duì)象 */
// keyPairGenerator.initialize(KEYSIZE, secureRandom);
keyPairGenerator.initialize(KEYSIZE);
/** 生成密匙對(duì) */
KeyPair keyPair = keyPairGenerator.generateKeyPair();
/** 得到公鑰 */
Key publicKey = keyPair.getPublic();
/** 得到私鑰 */
Key privateKey = keyPair.getPrivate();
ObjectOutputStream oos1 = null;
ObjectOutputStream oos2 = null;
try {
/** 用對(duì)象流將生成的密鑰寫入文件 */
oos1 = new ObjectOutputStream(new FileOutputStream(PUBLIC_KEY_FILE));
oos2 = new ObjectOutputStream(new FileOutputStream(PRIVATE_KEY_FILE));
oos1.writeObject(publicKey);
oos2.writeObject(privateKey);
} catch (Exception e) {
throw e;
}
finally{
/** 清空緩存，關(guān)閉文件輸出流 */
oos1.close();
oos2.close();
}
}
/**
* 加密方法
* @param source 源數(shù)據(jù)
* @return
* @throws Exception
*/
public static String encrypt(String source) throws Exception {
generateKeyPair();
Key publicKey;
ObjectInputStream ois = null;
try {
/** 將文件中的公鑰對(duì)象讀出 */
ois = new ObjectInputStream(new FileInputStream(
PUBLIC_KEY_FILE));
publicKey = (Key) ois.readObject();
} catch (Exception e) {
throw e;
}
finally{
ois.close();
}
/** 得到Cipher對(duì)象來(lái)實(shí)現(xiàn)對(duì)源數(shù)據(jù)的RSA加密 */
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
byte[] b = source.getBytes();
/** 執(zhí)行加密操作 */
byte[] b1 = cipher.doFinal(b);
BASE64Encoder encoder = new BASE64Encoder();
return encoder.encode(b1);
}
/**
* 解密算法
* @param cryptograph 密文
* @return
* @throws Exception
*/
public static String decrypt(String cryptograph) throws Exception {
Key privateKey;
ObjectInputStream ois = null;
try {
/** 將文件中的私鑰對(duì)象讀出 */
ois = new ObjectInputStream(new FileInputStream(
PRIVATE_KEY_FILE));
privateKey = (Key) ois.readObject();
} catch (Exception e) {
throw e;
}
finally{
ois.close();
}
/** 得到Cipher對(duì)象對(duì)已用公鑰加密的數(shù)據(jù)進(jìn)行RSA解密 */
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, privateKey);
BASE64Decoder decoder = new BASE64Decoder();
byte[] b1 = decoder.decodeBuffer(cryptograph);
/** 執(zhí)行解密操作 */
byte[] b = cipher.doFinal(b1);
return new String(b);
}
public static void main(String[] args) throws Exception {
String source = "恭喜發(fā)財(cái)!";// 要加密的字符串
System.out.println("準(zhǔn)備用公鑰加密的字符串為：" + source);
String cryptograph = encrypt(source);// 生成的密文
System.out.print("用公鑰加密后的結(jié)果為:" + cryptograph);
System.out.println();
String target = decrypt(cryptograph);// 解密密文
System.out.println("用私鑰解密后的字符串為：" + target);
System.out.println();
}
}
http://blog.sina.com.cn/s/blog_43b03c72010080t2.html
http://topic.csdn.net/t/20040510/14/3049788.html
http://yuanliyin.iteye.com/blog/853334