java RSA加解密以及用途

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.math.BigInteger;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;import org.apache.commons.codec.binary.Base64;public class RSAUtils {
/**
* 生成公钥和私钥, 一般一次性生成, 存储在文件中进行分发和使用
*/
public static void generateKey() {
try {
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(1024); //一般来说, 长度为2048是最好的, 也是推荐的
KeyPair kp = kpg.genKeyPair();
PublicKey pbkey = kp.getPublic();
PrivateKey prkey = kp.getPrivate();
// 保存公钥
FileOutputStream f1 = new FileOutputStream("d:/pubkey.dat");
ObjectOutputStream b1 = new ObjectOutputStream(f1);
b1.writeObject(pbkey);
// 保存私钥
FileOutputStream f2 = new FileOutputStream("d:/privatekey.dat");
ObjectOutputStream b2 = new ObjectOutputStream(f2);
b2.writeObject(prkey);
} catch (Exception e) {
}
} /**
* 公钥加密, 一般调用者传递明文, 从本地存储读取公钥进行加密
* @param plainTxt
* @return
* @throws Exception
*/
public static String pubEncrypt(String plainTxt) throws Exception {
String s = Base64.encodeBase64String(plainTxt.getBytes("UTF-8"));
// 获取公钥及参数e,n
FileInputStream f = new FileInputStream("d:/pubkey.dat");
ObjectInputStream b = new ObjectInputStream(f);
RSAPublicKey pbk = (RSAPublicKey) b.readObject();
BigInteger e = pbk.getPublicExponent();
BigInteger n = pbk.getModulus();
// 获取明文m
byte ptext[] = s.getBytes("UTF-8");
BigInteger m = new BigInteger(ptext);
// 计算密文c
BigInteger c = m.modPow(e, n);
// 保存密文
String ciperTxt = c.toString();
return ciperTxt;
} /**
* 私钥解密, 一般调用者传递密文, 从本地存储读取私钥进行解密
* @param ciperTxt
* @return
* @throws Exception
*/
public static String privDecrypt(String ciperTxt) throws Exception {
BigInteger c = new BigInteger(ciperTxt);
// 读取私钥
FileInputStream f = new FileInputStream("d:/privatekey.dat");
ObjectInputStream b = new ObjectInputStream(f);
RSAPrivateKey prk = (RSAPrivateKey) b.readObject();
BigInteger d = prk.getPrivateExponent();
// 获取私钥参数及解密
BigInteger n = prk.getModulus();
BigInteger m = c.modPow(d, n);
// 显示解密结果
byte[] mt = m.toByteArray();
String plainTxt = new String(Base64.decodeBase64(mt),"UTF-8");
return plainTxt;
}
public static void main(String args[]) {
try {
// generateKey();
String ciperTxt = pubEncrypt("测试大中华123区");
System.out.println("公钥加密密文：" + ciperTxt);
System.out.println("私钥解密：" + privDecrypt(ciperTxt));
} catch (Exception e) {
System.out.println(e.toString());
}
}
}