DSA数字签名例子

1、DSA公钥私钥生成类：

import java.io.FileNotFoundException;   
import java.io.FileOutputStream;   
import java.io.IOException;   
import java.io.ObjectOutputStream;   
import java.security.KeyPair;   
import java.security.KeyPairGenerator;   
import java.security.NoSuchAlgorithmException;   
import java.security.SecureRandom;   
  
/**
 * <p>
 * Title:  * 生成DSA密钥对的工具类  
 * 使用方法：java DSAKeyPairGenerator -genkey public.key private.key  
 * public.key--生成的公钥文件名  
 * private.key--生成的私钥文件名  
 * </p>
 * 
 * <p>
 * Description: 
 * </p>
 * 
 * <p>
 * Copyright: 融博技术有限公司 2012
 * </p>
 * 
 * @author 袁泉锋HO174959
 * @version 1.0
 * @date Jul 30, 2012
 *
 */
public class DSAKeyPairGenerator {   
    private static final int KEYSIZE=512;   
    /**  
     * 生成DSA密钥对的工具类  
     * 使用方法：java DSAKeyPairGenerator -genkey public.key private.key  
     * public.key--生成的公钥文件名  
     * private.key--生成的私钥文件名  
     * @param args  
     */  
    public static void main(String[] args) {   
        if(args[0].equals("-genkey")){   
            try {   
                KeyPairGenerator pairgen=KeyPairGenerator.getInstance("DSA");   
                SecureRandom random=new SecureRandom();   
                pairgen.initialize(KEYSIZE, random);   
                KeyPair keyPair=pairgen.generateKeyPair();   
                   
                ObjectOutputStream out=new ObjectOutputStream(new FileOutputStream(args[1]));   
                out.writeObject(keyPair.getPublic());   
                out.close();   
                   
                out=new ObjectOutputStream(new FileOutputStream(args[2]));   
                out.writeObject(keyPair.getPrivate());   
                out.close();   
            } catch (NoSuchAlgorithmException e) {   
                // TODO 自动生成 catch 块   
                e.printStackTrace();   
            } catch (FileNotFoundException e) {   
                // TODO 自动生成 catch 块   
                e.printStackTrace();   
            } catch (IOException e) {   
                // TODO 自动生成 catch 块   
                e.printStackTrace();   
            }   
        }   
    }   
  
}  

 

 

2、DSA服务类

import java.io.ObjectInputStream;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
  
  
/**
 * <p>
 * Title: 签名服务类
 * </p>
 * 
 * <p>
 * Description: 
 * </p>
 * 
 * <p>
 * Copyright: 融博技术有限公司 2012
 * </p>
 * 
 * @author 袁泉锋HO174959
 * @version 1.0
 * @date Jul 30, 2012
 *
 */
public class DSAService {   
	private PublicKey publicKey;    //公钥  给对方的
    private PrivateKey privateKey;    //私钥  自己保存好
	public DSAService() throws Exception	{
		try {   
            ObjectInputStream keyIn = new ObjectInputStream(DSAService.class.getResourceAsStream("/bb.key"));   
            privateKey = (PrivateKey) keyIn.readObject();   
            keyIn.close();   
            ObjectInputStream keyIn2 = new ObjectInputStream(DSAService.class.getResourceAsStream("/aa.key")); 
            publicKey = (PublicKey) keyIn2.readObject();   
            keyIn2.close();   
		} catch (Exception e) {   
            throw e;   
        }   
	}
    /**
     * <Description>对内容进行签名
     *
     * @since Jul 30, 2012
     * @param content
     * @return
     * @throws Exception <Description>
     *
     */
    public String sign(String content) throws Exception {   
        try {   
            Signature signalg = Signature.getInstance("DSA");   
            signalg.initSign(privateKey);   
            signalg.update(content.getBytes());   
            byte[] signature = signalg.sign();   
            return encodeHex(signature);   
        } catch (Exception e) {   
        	e.printStackTrace();
            throw e;   
        }   
    }   
  
    /**
     * <Description>对明文进行验签,确定contecnt是否是对方的信息
     *
     * @since Jul 30, 2012
     * @param signature
     * @param contecnt
     * @return
     * @throws Exception <Description>
     *
     */
    public boolean verify(String signature, String contecnt) throws Exception {   
        try {   
            Signature verifyalg = Signature.getInstance("DSA");   
            verifyalg.initVerify(publicKey);   
  
            verifyalg.update(contecnt.getBytes());   
  
            return verifyalg.verify(decodeHex(signature));   
        } catch (Exception e) {   
        	e.printStackTrace();
        	throw e;   
        }   
    }   
    /**
     * <Description>把二进制对象转化为16进制串（用字符串表示）
     *
     * @since Jul 30, 2012
     * @param bytes
     * @return <Description>
     *
     */
    private  String encodeHex(byte[] bytes) {
		StringBuffer buf = new StringBuffer(bytes.length * 2);
		for (int i = 0; i < bytes.length; ++i) {
			if ((bytes[i] & 0xFF) < 16) {
				buf.append("0");
			}
			buf.append(Long.toString(bytes[i] & 0xFF, 16));
		}
		return buf.toString();
	}
    /**
     * <Description>把字符串（该串标表示的是16进制）转化为二进制对象
     *
     * @since Jul 30, 2012
     * @param hex
     * @return <Description>
     *
     */
    private byte[] decodeHex(String hex) {
		char[] chars = hex.toCharArray();
		byte[] bytes = new byte[chars.length / 2];
		int byteCount = 0;
		for (int i = 0; i < chars.length; i += 2) {
			byte newByte = 0;
			newByte = (byte) (newByte | hexCharToByte(chars[i]));
			newByte = (byte) (newByte << 4);
			newByte = (byte) (newByte | hexCharToByte(chars[(i + 1)]));
			bytes[byteCount] = newByte;
			++byteCount;
		}
		return bytes;
	}
	private byte hexCharToByte(char ch) {
		switch (ch) {
		case '0':
			return 0;
		case '1':
			return 1;
		case '2':
			return 2;
		case '3':
			return 3;
		case '4':
			return 4;
		case '5':
			return 5;
		case '6':
			return 6;
		case '7':
			return 7;
		case '8':
			return 8;
		case '9':
			return 9;
		case 'a':
			return 10;
		case 'b':
			return 11;
		case 'c':
			return 12;
		case 'd':
			return 13;
		case 'e':
			return 14;
		case 'f':
			return 15;
		}
		return 0;
	}
	public static void main(String[] aa){
		try {
			DSAService ss = new DSAService();
			String dd = ss.sign("yqf"); //对"yqf"签名
			System.out.println(dd); //签名后
			boolean isSucc = ss.verify(dd, "yqf"); //对明文进行验签
			System.out.println(isSucc); 
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	} 
}  

 

 

 

通过例子，不难发现，DSA只能做签名，不是做加密用的。

签名是什么概念，就是说，你收到一个东西，你要验证下是不是你希望的那个人发送过来的，否则我不要，这就是签名。