package tsoffice;
 
 
import javax.crypto.Cipher;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;
import java.util.Base64;
 
public final class TestRSA
{
    private final static String ALGORITHM = "RSA";
    private static final String CHARSET   = "utf-8";
 
    /**
     * 密钥长度 于原文长度对应 以及越长速度越慢
     */
    private final static int KEY_SIZE = 512;
    /**
     * 用于封装随机产生的公钥与私钥
     */
    private static Map<Integer, String> keyMap = new HashMap<Integer, String>();
    /**
     * 随机生成密钥对
     */
    public static void genKeyPair() throws NoSuchAlgorithmException {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(ALGORITHM);
        keyPairGen.initialize(KEY_SIZE, new SecureRandom());
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        String publicKeyString = Base64.getEncoder().encodeToString(publicKey.getEncoded());
        String privateKeyString = Base64.getEncoder().encodeToString(privateKey.getEncoded());
        keyMap.put(0, publicKeyString);
        keyMap.put(1, privateKeyString);
    }
 
    public static String encrypt(String str, String publicKey) throws Exception {
        //base64编码的公钥
        byte[] decoded = Base64.getDecoder().decode(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance(ALGORITHM).generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        
        byte[] encrypted = cipher.doFinal(str.getBytes(CHARSET));
        System.out.println("encrypted="+encrypted.length);
        return Base64.getEncoder().encodeToString(encrypted);
    }
 
    public static String decrypt(String str, String privateKey) throws Exception {
        //64位解码加密后的字符串
        byte[] inputByte = Base64.getDecoder().decode(str);
        //base64编码的私钥
        byte[] decoded = Base64.getDecoder().decode(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance(ALGORITHM).generatePrivate(new PKCS8EncodedKeySpec(decoded));
        //RSA解密
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        return new String(cipher.doFinal(inputByte));
    }
    
    public static void main(String[] args) throws Exception {
        long temp = System.currentTimeMillis();
        //生成公钥和私钥
        genKeyPair();
        //加密字符串
        System.out.println("公钥:" + keyMap.get(0).length());
        System.out.println("私钥:" + keyMap.get(1).length());
        System.out.println("生成密钥消耗时间:" + (System.currentTimeMillis() - temp) / 1000.0 + "秒");
        
        String message = "RSA测试:泰山Office";
        
        System.out.println("原文:" + message);
        temp = System.currentTimeMillis();
        String messageEn = encrypt(message, keyMap.get(0));
        System.out.println("密文:" + messageEn);
        System.out.println("加密消耗时间:" + (System.currentTimeMillis() - temp) / 1000.0 + "秒");
        
        temp = System.currentTimeMillis();
        String messageDe = decrypt(messageEn, keyMap.get(1));
        System.out.println("解密:" + messageDe);
        System.out.println("解密消耗时间:" + (System.currentTimeMillis() - temp) / 1000.0 + "秒");
    }
}