package com.mstf.rsa;
 
import java.security.KeyFactory;
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 java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
 
import javax.crypto.Cipher;
 
import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
 
/*RSA 工具類。提供加密，解密，生成密鑰對等方法。
RSA加密原理概述 
RSA的安全性依賴于大數的分解，公鑰和私鑰都是兩個大素數（大于100的十進制位）的函數。
據猜測，從一個密鑰和密文推斷出明文的難度等同于分解兩個大素數的積 
密鑰的產生： 
 1.選擇兩個大素數 p,q ,計算 n=p*q; 
 2.隨機選擇加密密鑰 e ,要求 e 和 (p-1)*(q-1)互質 
 3.利用 Euclid 算法計算解密密鑰 d , 使其滿足 e*d = 1(mod(p-1)*(q-1)) (其中 n,d 也要互質) 
 4:至此得出公鑰為 (n,e) 私鑰為 (n,d) 
 RSA速度 
 * 由于進行的都是大數計算，使得RSA最快的情況也比DES慢上100倍，無論 是軟件還是硬件實現。 
 * 速度一直是RSA的缺陷。一般來說只用于少量數據 加密。*/
public class RSAsecurity {
 
 public static String src = "admin";
 
 public void priENpubDE() {
 
  try {
   // 初始化秘鑰
   KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
   // 秘鑰長度
   keyPairGenerator.initialize(1024);
   // 初始化秘鑰對
   KeyPair keyPair = keyPairGenerator.generateKeyPair();
   // 公鑰
   RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
   // 私鑰
   RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();
 
   // 2.私鑰加密，公鑰解密----加密
   // 生成私鑰
   PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
   KeyFactory keyFactory = KeyFactory.getInstance("RSA");
   PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
   // Cipher類為加密和解密提供密碼功能，通過getinstance實例化對象
   Cipher cipher = Cipher.getInstance("RSA");
   // 初始化加密
   cipher.init(Cipher.ENCRYPT_MODE, privateKey);
   byte[] result = cipher.doFinal(src.getBytes());
   System.out.println("私鑰加密，公鑰解密----加密:" + Base64.encode(result));
 
   // 3.私鑰加密，公鑰解密----解密
   // 生成公鑰
   X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
   keyFactory = KeyFactory.getInstance("RSA");
   PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
   cipher = Cipher.getInstance("RSA");
   // 初始化解密
   cipher.init(Cipher.DECRYPT_MODE, publicKey);
   result = cipher.doFinal(result);
   System.out.println("私鑰加密，公鑰解密----解密:" + new String(result));
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 
 }
 
 public void pubENpriDE() {
  try {
   // 1.初始化秘鑰
   KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
   // 秘鑰長度
   keyPairGenerator.initialize(512);
   // 初始化秘鑰對
   KeyPair keyPair = keyPairGenerator.generateKeyPair();
   // 公鑰
   RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
   // 私鑰
   RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();
 
   // 2.公鑰加密，私鑰解密----加密
   X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
   KeyFactory keyFactory = KeyFactory.getInstance("RSA");
   PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
   // 初始化加密
   // Cipher類為加密和解密提供密碼功能，通過getinstance實例化對象
   Cipher cipher = Cipher.getInstance("RSA");
   cipher.init(Cipher.ENCRYPT_MODE, publicKey);
   // 加密字符串
   byte[] result = cipher.doFinal(src.getBytes());
   System.out.println("公鑰加密，私鑰解密----加密:" + Base64.encode(result));
 
   // 3.公鑰加密，私鑰解密-----解密
   PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
   keyFactory = KeyFactory.getInstance("RSA");
   PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
   // 初始化解密
   cipher.init(Cipher.DECRYPT_MODE, privateKey);
   // 解密字符串
   result = cipher.doFinal(result);
   System.out.println("公鑰加密，私鑰解密-----解密:" + new String(result));
 
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 
 }
}

package com.mstf.rsa;
 
import com.mstf.rsa.RSAsecurity;
 
public class RSAtest {
 public static void main(String[] args) {
  RSAsecurity rsAsecurity = new RSAsecurity();
  System.out.println("私鑰加密公鑰解密例：");
  rsAsecurity.priENpubDE();
  System.out.println("公鑰加密私鑰解密例：");
  rsAsecurity.pubENpriDE();
 }
}