Rsa是非对称算法，他可以产生密钥对，可以用公钥加密，私钥解密，或者私钥加密，公钥解密，最大程度的保障安全性，也可以用私钥签名，公钥验证签名的正确性，防止拥有私钥的人抵赖。下面展示加解密算法和RSA签名验证。
产生密钥对的类：
/**
*
*/
package com.spell.rsa;
import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
/**
* 产生公钥和私钥对，并且保存在文件中，公钥 pk.dat，私钥 sk.dat
*
* @author Administrator
*
*/
public class KeyGen {
/**
*
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
// 加密的种子信息
String keyInfo = "ASDFSDFNUGD__TYTY";
KeyGen kg = new KeyGen();
kg.genKeys(keyInfo);
}
/**
* 根据keyInfo产生公钥和私钥，并且保存到pk.dat和sk.dat文件中
*
* @param keyInfo
* @throws Exception
*/
public void genKeys(String keyInfo) throws Exception {
KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA");
SecureRandom random = new SecureRandom();
random.setSeed(keyInfo.getBytes());
// 初始加密，长度为512，必须是大于512才可以的
keygen.initialize(512, random);
// 取得密钥对
KeyPair kp = keygen.generateKeyPair();
// 取得公钥
PublicKey publicKey = kp.getPublic();
System.out.println(publicKey);
saveFile(publicKey, "pk.dat");
// 取得私钥
PrivateKey privateKey = kp.getPrivate();
saveFile(privateKey, "sk.dat");
}
/**
* 保存对象到文件
*
* @param obj
* @param fileName
* @throws Exception
*/
private void saveFile(Object obj, String fileName) throws Exception {
ObjectOutputStream output = new ObjectOutputStream(
new FileOutputStream(fileName));
output.writeObject(obj);
output.close();
}
}
利用公钥加密，私钥解密：
package com.spell.rsa;
import java.io.FileInputStream;
import java.io.ObjectInputStream;
import java.security.Key;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import javax.crypto.Cipher;
/**
* RSA加解密,RSA签名、签名验证类
*
* @author Administrator
*
*/
public class RsaMessage {
public static void main(String[] args) throws Exception {
String str = "hello,有中文的情况";
System.out.println("原文：" + str);
RsaMessage rsa = new RsaMessage();
RSAPrivateKey privateKey = (RSAPrivateKey) rsa.readFromFile("sk.dat");
RSAPublicKey publickKey = (RSAPublicKey) rsa.readFromFile("pk.dat");
byte[] encbyte = rsa.encrypt(str, privateKey);
System.out.println("私钥加密后：");
String encStr = toHexString(encbyte);
System.out.println(encStr);
byte[] signBytes = rsa.sign(str, privateKey);
System.out.println("签名值：");
String signStr = toHexString(signBytes);
System.out.println(signStr);
byte[] decByte = rsa.decrypt(encStr, publickKey);
System.out.println("公钥解密后：");
String decStr = new String(decByte);
System.out.println(decStr);
if (rsa.verifySign(str, signStr, publickKey)) {
System.out.println("rsa sign check success");
} else {
System.out.println("rsa sign check failure");
}
}
/**
* 加密,key可以是公钥，也可以是私钥
*
* @param message
* @return
* @throws Exception
*/
public byte[] encrypt(String message, Key key) throws Exception {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, key);
return cipher.doFinal(message.getBytes());
}
/**
* 解密，key可以是公钥，也可以是私钥，如果是公钥加密就用私钥解密，反之亦然
*
* @param message
* @return
* @throws Exception
*/
public byte[] decrypt(String message, Key key) throws Exception {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, key);
return cipher.doFinal(toBytes(message));
}
/**
* 用私钥签名
*
* @param message
* @param key
* @return
* @throws Exception
*/
public byte[] sign(String message, PrivateKey key) throws Exception {
Signature signetcheck = Signature.getInstance("MD5withRSA");
signetcheck.initSign(key);
signetcheck.update(message.getBytes("ISO-8859-1"));
return signetcheck.sign();
}
/**
* 用公钥验证签名的正确性
*
* @param message
* @param signStr
* @return
* @throws Exception
*/
public boolean verifySign(String message, String signStr, PublicKey key)
throws Exception {
if (message == null || signStr == null || key == null) {
return false;
}
Signature signetcheck = Signature.getInstance("MD5withRSA");
signetcheck.initVerify(key);
signetcheck.update(message.getBytes("ISO-8859-1"));
return signetcheck.verify(toBytes(signStr));
}
/**
* 从文件读取object
*
* @param fileName
* @return
* @throws Exception
*/
private Object readFromFile(String fileName) throws Exception {
ObjectInputStream input = new ObjectInputStream(new FileInputStream(
fileName));
Object obj = input.readObject();
input.close();
return obj;
}
public static String toHexString(byte[] b) {
StringBuilder sb = new StringBuilder(b.length * 2);
for (int i = 0; i < b.length; i++) {
sb.append(HEXCHAR[(b[i] & 0xf0) >>> 4]);
sb.append(HEXCHAR[b[i] & 0x0f]);
}
return sb.toString();
}
public static final byte[] toBytes(String s) {
byte[] bytes;
bytes = new byte[s.length() / 2];
for (int i = 0; i < bytes.length; i++) {
bytes[i] = (byte) Integer.parseInt(s.substring(2 * i, 2 * i + 2),
16);
}
return bytes;
}
private static char[] HEXCHAR = { '0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
}
