对文件进行DSA数字签名

package com.ivan.security.algorithm;

/**
 * 对文件进行DSA数字签名
 * @author Ivan
 * @DataTime 2006-12-12 0:58
 *
 */

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;
import java.security.SignatureException;

import com.iuxi.security.util.Tool;

public class DSAUtil ...{
    
    private PublicKey pubKey;
    private PrivateKey priKey;
    public String pubfile = "";
    public String prifile = "";
    
    public DSAUtil() ...{}
    public DSAUtil(String pubfile, String prifile) ...{
        this.pubfile = pubfile;
        this.prifile = prifile;
    }
    
    /** *//**
     * 采用DSA算法生成非对称密钥对
     *
     */
    public void genKeys() ...{
        try ...{
            KeyPairGenerator keygen = KeyPairGenerator.getInstance("DSA");
            SecureRandom secrand = new SecureRandom();
            secrand.setSeed("random generator".getBytes());
            keygen.initialize(512,secrand);            //初始化密钥生成器
            KeyPair keys = keygen.generateKeyPair();//生成密钥对
            pubKey = keys.getPublic();
            priKey = keys.getPrivate();
        }catch(NoSuchAlgorithmException ex) ...{
            ex.printStackTrace();
        }
    }
    
    public String getPrifile() ...{
        return prifile;
    }
    public void setPrifile(String prifile) ...{
        this.prifile = prifile;
    }
    public String getPubfile() ...{
        return pubfile;
    }
    public void setPubfile(String pubfile) ...{
        this.pubfile = pubfile;
    }
    
    /** *//**
     * 保存密钥对信息到磁盘
     * @param filepath1 公钥的存放路径
     * @param filepath2 私钥的存放路径
     */
    public void saveKeys() ...{
        if((!pubfile.equals(""))&&(!prifile.equals("")))
            this.saveKeys(pubfile,prifile);
        else
            System.err.println("保存密钥出错，请先设置保存路径！");
    }
    public void saveKeys(String filepath1, String filepath2) ...{
        try ...{
            FileOutputStream fos = new FileOutputStream(filepath1);
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(pubKey);
            oos.close();
            fos = new FileOutputStream(filepath2);
            oos = new ObjectOutputStream(fos);
            oos.writeObject(priKey);
            oos.close();
        }catch(IOException ex) ...{
            System.err.println("保存密钥对信息出错！");
            ex.printStackTrace();
        }
    }
    
    /** *//**
     * 从磁盘读取密钥信息
     * @param filepath 密钥存放路径
     * @return 返回密钥信息，为 Object 类，然后可根据具体的 PublicKey 或 PrivateKey 进行强制类型转换
     */
    private Object getKey(String filepath) ...{
        Object obj = null;
        try ...{
            FileInputStream fis = new FileInputStream(filepath);
            ObjectInputStream ois = new ObjectInputStream(fis);
            obj = ois.readObject();
            ois.close();
        }catch(IOException ex) ...{
            System.err.println("读取密钥信息错误！");
        }catch(ClassNotFoundException ex) ...{
            ex.printStackTrace();
        }
        return obj;
    }
    
    /** *//**
     * 获取公钥，如果当前公钥为空，则从磁盘文件读取，并将其设置为当前公钥，否则直接返回当前公钥
     * @return 公钥
     */
    public PublicKey getPubKey() ...{
        if(pubKey != null)
            return pubKey;
        if(!pubfile.equals("")) ...{
            pubKey = (PublicKey)this.getKey(pubfile);
            return this.pubKey;
        }
        else ...{
            System.err.println("读取公钥信息错误!");
            return null;
        }
    }
    public PublicKey getPubKey(String filepath) ...{
        pubKey = (PublicKey)this.getKey(filepath);
        return this.pubKey;
    }
    
    /** *//**
     * 获取私钥，如果当前私钥为空，则从磁盘文件读取，并将其设置为当前私钥，否则直接返回当前私钥
     * @return 私钥
     */
    public PrivateKey getPriKey() ...{
        if(priKey != null)
            return priKey;
        if(!prifile.equals("")) ...{
            priKey = (PrivateKey)this.getKey(pubfile);
            return this.priKey;
        }
        else ...{
            System.err.println("读取私钥信息错误!");
            return null;
        }
    }
    public PrivateKey getPriKey(String filepath) ...{
        priKey = (PrivateKey)this.getKey(filepath);
        return this.priKey;
    }
    
    /** *//**
     * 利用当前私钥对信息进行签名
     * @return 签名信息（byte类型）
     */
    public byte[] signBytes(byte[] info) ...{
        byte[] signed = null;
        if(priKey == null) ...{
            System.err.println("======== 提取密钥信息错误，无法完成签名 =========");
            return null;
        }
        try ...{
            Signature signet = Signature.getInstance("DSA");
            signet.initSign(priKey);
            signet.update(info);
            signed = signet.sign();
        }catch(NoSuchAlgorithmException ex) ...{
            ex.printStackTrace();
        }catch(InvalidKeyException ex) ...{
            System.err.println("签名错误，无效的密钥");
            ex.printStackTrace();
        }catch(SignatureException ex) ...{
            ex.printStackTrace();
        }
        return signed;
    }
    
    /** *//**
     * 验证签名信息
     * @param info 待验证的信息
     * @param signed 该验证信息的签名
     * @return 若验证正常，则返回 true ,　否则返回 false
     */
    public boolean checkSign(byte[] info, byte[] signed) ...{
        if(pubKey == null) ...{
            System.err.println("======== 提取密钥信息错误，无法完成签名 =========");
            return false;
        }
        try ...{
            Signature checkSignet = Signature.getInstance("DSA");
            checkSignet.initVerify(pubKey);
            checkSignet.update(info);
            if(checkSignet.verify(signed)) ...{
                System.out.println("======== 签名正常 =========");
                return true;
            }
            else ...{
                System.err.println("======== 签名信息异常 =========");
                return false;
            }
        }catch(NoSuchAlgorithmException ex) ...{
            ex.printStackTrace();
        }catch(InvalidKeyException ex) ...{
            System.err.println("验证签名错误，无效的密钥");
            ex.printStackTrace();
        }catch(SignatureException ex) ...{
            ex.printStackTrace();
        }
        return true;
    }
    
    public static void main(String[] args) ...{
        DSAUtil dsa = new DSAUtil("pubKey.dat","priKey.dat");
        dsa.genKeys();
        dsa.saveKeys();
        String test = "This is just a test!";
        byte[] signedData = dsa.signBytes(test.getBytes());
        System.out.println(Tool.byte2hex(signedData));
        dsa.checkSign(test.getBytes(),signedData);
    }
}