package test;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
public class DSA {
	public static void main(String[] args) {
		try {
			DSA my = new DSA();
			my.run();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	public void run() {
		// 數(shù)字簽名生成密鑰
		// 第一步生成密鑰對(duì),如果已經(jīng)生成過 , 本過程就可以跳過
		// 對(duì)用戶來講 myprikey.dat 要保存在本地，而 mypubkey.dat 給發(fā)布給其它用戶
		if ((new java.io.File("myprikey.dat")).exists() == false) {
			if (generatekey() == false) {
				System.out.println("生成密鑰對(duì)敗");
				return;
			}
		}
		// 第二步 , 此用戶
		// 從文件中讀入私鑰 , 對(duì)一個(gè)字符串進(jìn)行簽名后保存在一個(gè)文件 (myinfo.dat) 中
		// 并且再把 myinfo.dat 發(fā)送出去，為了方便數(shù)字簽名也放進(jìn)了 myifno.dat 文件中 , 當(dāng)然也可分別發(fā)送
		try {
			ObjectInputStream in = new ObjectInputStream(new FileInputStream("myprikey.dat"));
			PrivateKey myprikey = (PrivateKey) in.readObject();
			in.close();
			String myinfo = "這是我的信息"; // 要簽名的信息
			// 用私鑰對(duì)信息生成數(shù)字簽名
			Signature signet = Signature.getInstance("DSA");
			signet.initSign(myprikey);
			signet.update(myinfo.getBytes());
			byte[] signed = signet.sign(); // 對(duì)信息的數(shù)字簽名
			System.out.println("signed( 簽名內(nèi)容 )=" + byte2hex(signed));
			// 把信息和數(shù)字簽名保存在一個(gè)文件中
			ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("myinfo.dat"));
			out.writeObject(myinfo);
			out.writeObject(signed);
			out.close();
			System.out.println("簽名并生成文件成功");
		} catch (java.lang.Exception e) {
			e.printStackTrace();
			System.out.println("簽名并生成文件失敗");
		}
		// 第三步 獲得信息檢查
		// 其他人通過公共方式得到此戶的公鑰和文件
		// 其他人用此戶的公鑰 , 對(duì)文件進(jìn)行檢查 , 如果成功說明是此用戶發(fā)布的信息 .
		try {
			ObjectInputStream in = new ObjectInputStream(new FileInputStream("mypubkey.dat"));
			PublicKey pubkey = (PublicKey) in.readObject();
			in.close();
			System.out.println(pubkey.getFormat());
			in = new ObjectInputStream(new FileInputStream("myinfo.dat"));
			String info = (String) in.readObject();
			byte[] signed = (byte[]) in.readObject();
			in.close();
			Signature signetcheck = Signature.getInstance("DSA");
			signetcheck.initVerify(pubkey);
			signetcheck.update(info.getBytes());
			if (signetcheck.verify(signed)) {
				System.out.println("info=" + info);
				System.out.println("簽名正常");
			} else
				System.out.println("非簽名正常");
		} catch (java.lang.Exception e) {
			e.printStackTrace();
		}
		;
	}
	// 生成一對(duì)文件 myprikey.dat 和 mypubkey.dat 私鑰和公鑰
	// 公鑰要用戶發(fā)送 ( 文件 , 網(wǎng)絡(luò)等方法 ) 給其它用戶 , 私鑰保存在本地
	public boolean generatekey() {
		try {
			KeyPairGenerator keygen = KeyPairGenerator.getInstance("DSA");
			keygen.initialize(512);
			KeyPair keys = keygen.genKeyPair();
			PublicKey pubkey = keys.getPublic();
			PrivateKey prikey = keys.getPrivate();
			ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("myprikey.dat"));
			out.writeObject(prikey);
			out.close();
			System.out.println("寫入對(duì)象 prikeys ok");
			out = new ObjectOutputStream(new FileOutputStream("mypubkey.dat"));
			out.writeObject(pubkey);
			out.close();
			System.out.println("寫入對(duì)象 pubkeys ok");
			System.out.println("生成密鑰對(duì)成功");
			return true;
		} catch (java.lang.Exception e) {
			e.printStackTrace();
			System.out.println("生成密鑰對(duì)失敗");
			return false;
		}
	}
	public String byte2hex(byte[] b) {
		String hs = "";
		String stmp = "";
		for (int n = 0; n < b.length; n++) {
			stmp = (java.lang.Integer.toHexString(b[n] & 0XFF));
			if (stmp.length() == 1)
				hs = hs + "0" + stmp;
			else
				hs = hs + stmp;
			if (n < b.length - 1)
				hs = hs + ":";
		}
		return hs.toUpperCase();
	}
}