有公匙，如何用RSA解密

Question

我现有一个公匙，请问如何用RSA将一个字符串解密呢？

Answer 1

我有一个java的sourcecode,我的目的就是写一个C#的函数，能对他加密过的数据进行，不知道哪位高手能帮忙看看
package com.panyudc.util;import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.text.SimpleDateFormat;
import java.util.Date;import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;/**
 * 用RSA算法对数据进行加密和解密
 */
public class DataEncryptDecrypt
{
    private static PublicKey pubkey;    private static PrivateKey prikey;    /**
     * 初始化公钥和私钥
     *  
     */
    public static synchronized void initKey(String pubkeyfile, String prikeyfile) throws IOException,
            NoSuchAlgorithmException, InvalidKeySpecException
    {
        FileInputStream in = null;
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        byte[] enckey = null;        //读出公钥
        in = new FileInputStream(pubkeyfile);
        enckey = new byte[in.available()];
        in.read(enckey);
        in.close();
        X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(enckey);
        pubkey = keyFactory.generatePublic(pubKeySpec);
        //读出私钥
        in = new FileInputStream(prikeyfile);
        enckey = new byte[in.available()];
        in.read(enckey);
        in.close();
        PKCS8EncodedKeySpec priKeySpec = new PKCS8EncodedKeySpec(enckey);
        prikey = keyFactory.generatePrivate(priKeySpec);
    }    /**
     * 对数据data进行解密或者加密，opmode 决定是加密还是解密，keymode决定是用公钥还是私钥
     * 另外，进行加密时data后面附加了系统当前的时间，时间格式（yyyyMMddHHmmss）
     */
    public static String getData(String data, int opmode, int keymode) throws NoSuchPaddingException,
            InvalidKeyException, IllegalStateException, IllegalBlockSizeException, BadPaddingException,
            NoSuchAlgorithmException, NoSuchProviderException, IOException, ClassNotFoundException,
            InvalidKeySpecException
    {
        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        if (Cipher.ENCRYPT_MODE == opmode)//加密
        {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
            if (Cipher.PUBLIC_KEY == keymode)//用公钥加密
            {
                cipher.init(Cipher.ENCRYPT_MODE, pubkey);
            }
            else if (Cipher.PRIVATE_KEY == keymode)
            {
                cipher.init(Cipher.ENCRYPT_MODE, prikey);
            }
            return byte2hex(cipher.doFinal((data + sdf.format(new Date(System.currentTimeMillis()))).getBytes("UTF8")));
        }
        else
        //解密
        {
            if (Cipher.PRIVATE_KEY == keymode)//用私钥解密
            {
                cipher.init(Cipher.DECRYPT_MODE, prikey);
            }
            else if (Cipher.PUBLIC_KEY == keymode)//用公钥解密
            {
                cipher.init(Cipher.DECRYPT_MODE, pubkey);
            }
            return new String(cipher.doFinal(hex2byte(data)), "UTF8");
        }
    }    /**
     * 生成公、私密码对
     * 
     * @return
     */
    public static boolean generatekey(String pubkeyfile, String prikeyfile)
    {
        FileOutputStream out = null;
        try
        {
            KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA");
            keygen.initialize(1024);
            KeyPair keys = keygen.genKeyPair();
            PublicKey pubkey = keys.getPublic();
            PrivateKey prikey = keys.getPrivate();            out = new FileOutputStream(prikeyfile);
            out.write(prikey.getEncoded());
            out.close();            out = new FileOutputStream(pubkeyfile);
            out.write(pubkey.getEncoded());
            out.close();
            return true;
        }
        catch (Exception e)
        {
            e.printStackTrace();
            if (out != null)
            {
                try
                {
                    out.close();
                }
                catch (IOException e1)
                {
                    e1.printStackTrace();
                }
            }
            return false;
        }
    }    /*
     * 将byte换成hex字符串
     */
    public static String byte2hex(byte[] b)
    {
        String hs = "";
        String stmp = "";
        for (int n = 0; n < b.length; n++)
        {
            stmp = (Integer.toHexString(b[n] & 0XFF));
            if (stmp.length() == 1)
                hs = hs + "0" + stmp;
            else
                hs = hs + stmp;        }
        return hs.toUpperCase();
    }    /*
     * 将hex串换成byte数组
     */
    public static byte[] hex2byte(String s)
    {
        byte[] b = new byte[s.length() / 2];
        for (int i = 0; i < s.length() / 2; i++)
        {
            b[i] = (byte) Integer.parseInt(s.substring(2 * i, 2 * i + 2), 16);
        }
        return b;
    }    public static void main(String[] args) throws InvalidKeyException, NoSuchPaddingException, IllegalStateException,
            IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchProviderException,
            InvalidKeySpecException, IOException, ClassNotFoundException
    {    }
}

Answer 2

java 里好像可以用私匙加密，然后用公匙和数字证书X.509进行解密,.net里应该也可以实现吧

Answer 3

本来对于rsa来说公钥加密或者私钥加密之后，都可以使用另外的一个钥匙解密的。