公钥私钥

Posted 2020-10-03 向前爬的蜗牛

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 {
/** 指定加密算法为RSA */
private static final String ALGORITHM = "RSA";
/** 密钥长度，用来初始化 */
private static final int KEYSIZE = 1024;
/** 指定公钥存放文件 */
private static String PUBLIC_KEY_FILE = "PublicKey";
/** 指定私钥存放文件 */
private static String PRIVATE_KEY_FILE = "PrivateKey";

/**
* 生成密钥对
* @throws Exception
*/
private static void generateKeyPair() throws Exception {

// /** RSA算法要求有一个可信任的随机数源 */
// SecureRandom secureRandom = new SecureRandom();

/** 为RSA算法创建一个KeyPairGenerator对象 */
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);

/** 利用上面的随机数据源初始化这个KeyPairGenerator对象 */
// keyPairGenerator.initialize(KEYSIZE, secureRandom);
keyPairGenerator.initialize(KEYSIZE);

/** 生成密匙对 */
KeyPair keyPair = keyPairGenerator.generateKeyPair();

/** 得到公钥 */
Key publicKey = keyPair.getPublic();

/** 得到私钥 */
Key privateKey = keyPair.getPrivate();

ObjectOutputStream oos1 = null;
ObjectOutputStream oos2 = null;
try {
/** 用对象流将生成的密钥写入文件 */
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{
/** 清空缓存，关闭文件输出流 */
oos1.close();
oos2.close();
}
}

/**
* 加密方法
* @param source 源数据
* @return
* @throws Exception
*/
public static String encrypt(String source) throws Exception {
generateKeyPair();
Key publicKey;
ObjectInputStream ois = null;
try {
/** 将文件中的公钥对象读出 */
ois = new ObjectInputStream(new FileInputStream(
PUBLIC_KEY_FILE));
publicKey = (Key) ois.readObject();
} catch (Exception e) {
throw e;
}
finally{
ois.close();
}

/** 得到Cipher对象来实现对源数据的RSA加密 */
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
byte[] b = source.getBytes();
/** 执行加密操作 */
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 {
/** 将文件中的私钥对象读出 */
ois = new ObjectInputStream(new FileInputStream(
PRIVATE_KEY_FILE));
privateKey = (Key) ois.readObject();
} catch (Exception e) {
throw e;
}
finally{
ois.close();
}

/** 得到Cipher对象对已用公钥加密的数据进行RSA解密 */
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, privateKey);
BASE64Decoder decoder = new BASE64Decoder();
byte[] b1 = decoder.decodeBuffer(cryptograph);

/** 执行解密操作 */
byte[] b = cipher.doFinal(b1);
return new String(b);
}

public static void main(String[] args) throws Exception {
String source = "恭喜发财!";// 要加密的字符串
System.out.println("准备用公钥加密的字符串为：" + source);

String cryptograph = encrypt(source);// 生成的密文
System.out.print("用公钥加密后的结果为:" + cryptograph);
System.out.println();

String target = decrypt(cryptograph);// 解密密文
System.out.println("用私钥解密后的字符串为：" + target);
System.out.println();
}
}