典型的非對稱加密算法 RSA

ps:

RES算法僅僅需要一套祕鑰既可以完成加密/解密算法，並且公鑰的祕鑰長度明顯的小於私鑰的祕鑰長度，支持“公鑰加密，私鑰解密”和“私鑰加密，公鑰解密”這兩項加密解密原則。

代碼樣例：

package encrypt.util;

import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
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 javax.crypto.Cipher;

import org.apache.commons.codec.binary.Base64;
import org.apache.commons.codec.binary.Hex;


/**
 * RSA安全編碼組件
 * @author admin
 *
 */
public class RSACoder {
    //非對稱加密祕鑰算法
    private static final String KEY_ALGORITHM = "RSA";
    //公鑰
    private static final String PUBLIC_KEY = "RSAPublicKey";
    //私鑰
    private static final String PRIVATE_KEY = "RSAPrivateKey";
    //RSA祕鑰長度  默認1024
    private static final int KEY_SIZE = 1024;
    
    //私鑰解密
    /**
     * @param data 待解密的數據
     * @param key  私鑰
     * @return byte[] 解密數據
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(byte[] data,byte[] key) throws Exception{
        //取的私鑰
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(key);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        //生產私鑰對象
        PrivateKey  privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
        
        //對數據解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        
        //執行
        return cipher.doFinal(data);
    }
    
    /**
     * @param data 待加密數據
     * @param key  公鑰
     * @return byte[] 加密數據
     * @throws Exception
     */
    public static byte[] encryptByPublicKey(byte[] data,byte[] key) throws Exception{
        //取的公鑰
        X509EncodedKeySpec X509KeySpec = new X509EncodedKeySpec(key);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        //生產公鑰對象
        PublicKey  publicKey = keyFactory.generatePublic(X509KeySpec);
        //對數據進行加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        //執行
        return cipher.doFinal(data);
    }
    
    /**取的私鑰
     * @param keyMap 祕鑰map
     * @return byte[] 私鑰
     */
    public static byte[] getPrivateKey(Map<String,Object> keyMap){
        Key key = (Key)keyMap.get(PRIVATE_KEY);
        return key.getEncoded();
    }
    
    /**取的公鑰
     * @param keyMap 祕鑰map
     * @return byte[] 公鑰
     */
    public static byte[] getPublicKey(Map<String,Object> keyMap){
        Key key = (Key)keyMap.get(PUBLIC_KEY);
        return key.getEncoded();
    }
    
    private static Map<String,Object> initKey() throws Exception{
        //實例化祕鑰生產器
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        //初始化祕鑰生產器
        keyPairGen.initialize(KEY_SIZE);
        //生產祕鑰對
        KeyPair keyPair = keyPairGen.generateKeyPair();
        //公鑰
        RSAPublicKey publicKey = (RSAPublicKey)keyPair.getPublic();
        //祕鑰
        RSAPrivateKey privateKey = (RSAPrivateKey)keyPair.getPrivate();
        
        //封裝祕鑰
        Map<String,Object> keyMap = new HashMap<String,Object>();
        keyMap.put(PUBLIC_KEY, publicKey);
        keyMap.put(PRIVATE_KEY, privateKey);
        return keyMap;
    }
    
    
    /**
     * 將16進制字符串還原爲字節數組.
     */
    private static final byte[] hexStrToBytes(String s) {
        byte[] bytes;

        bytes = new byte[s.length() / 2];

        for (int i = 0; i < bytes.length; i++) {
            bytes[i] = (byte) Integer.parseInt(s.substring(2 * i, 2 * i + 2), 16);
        }

        return bytes;
    }
    
    
    public static void main(String[] args) throws Exception {
    /*    Map<String,Object> keyMap = RSACoder.initKey();
        byte[] privateKey = RSACoder.getPrivateKey(keyMap);
        byte[] publicKey = RSACoder.getPublicKey(keyMap);
        
        //Hex.encodeHex 做16進制編碼處理
        System.out.println("16進制 公鑰字符串：\t"+new String(Hex.encodeHex(publicKey)));
        System.out.println("16進制 私鑰字符串：\t"+new String(Hex.encodeHex(privateKey)));*/
        
        String privateKeyString = "30820276020100300d06092a864886f70d0101010500048202603082025c02010002818100820afd22bdd36cb75ef8db1a970d50ca352d57eecaa28779a559f626bf9182f0f986a2ea251f76040616032dc739e8558c0dfdfa82bef0203e8412bb2cb0dcaf7f568f100ce05f7bb239a6a4cbd7c1ed8041ea6f3b0c641c94f71228320584ba871012df218799b09f638478b9233bf594faa22d30d792a46b58459a52a1e1ef02030100010281803f5d97671c542f3f52d9b3f9caecc41723be4a80a2e07b5efd014efe268e82dd64d903fd4fc57abe0f311eaf69ca7fb95f9b59cc7d750890cda59172ff1dd70a3a7dae06661b1b7d5785a5153e4716b6c8fe1e2d8f8afc31e97b29d5a59365379a8949ebdf6543d293ec87a43d63ffa6507aa20dd5995efbdaa28c6198991231024100f8a68afdd0a358e2314d35c47a814b548383e2ce53e3eeff18ee844c8983ff40a0c80a4560efb0ffbd1c8b7092b38d75fa3190798c648b73825b11401a44d09502410085e2fb1bad7ffbad70cd6d992f22f504f4d09217b9eca3e4793810cb2a389cd828f091cd625fbc3fa0da7b0178dc3fcdbb94dc77db9c051ceb80c79d7060b373024100bb8c22da3f3c761666496e7cbc4a399f8d7334e79baf18dda0d887419397d437d30e0f71352495c4cfc7700581219d5997553b3bf301038e248cbbfe35d221e10240237c4785cc74716644d18dccddfb6be98661897714662e022e46b7dcc13204101eb9b44b35599e7156d6d167507b3fc5ed83c4f35797809b6ba7d4405c3aa515024055daef13aa8d7ccc927df4b1013e02a148666fece687a8be06a6c9beccf2055c96e0f0f4911fbdffdcf948a886c9e879a828f9962df0cf60b2bcf1d0a2098a8a";
        String publicKeyString = "30819f300d06092a864886f70d010101050003818d0030818902818100820afd22bdd36cb75ef8db1a970d50ca352d57eecaa28779a559f626bf9182f0f986a2ea251f76040616032dc739e8558c0dfdfa82bef0203e8412bb2cb0dcaf7f568f100ce05f7bb239a6a4cbd7c1ed8041ea6f3b0c641c94f71228320584ba871012df218799b09f638478b9233bf594faa22d30d792a46b58459a52a1e1ef0203010001";
        byte[] privateKey = hexStrToBytes(privateKeyString);
        byte[] publicKey = hexStrToBytes(publicKeyString);
        
        
        System.out.println("公鑰：\t"+Base64.encodeBase64String(publicKey));
        System.out.println("私鑰：\t"+Base64.encodeBase64String(privateKey));
        
        String str = "RSA";
        byte[] inputStr = str.getBytes();
        System.out.println("原文：\t"+str);
        
        //公鑰加密
        byte[] endcryptData = RSACoder.encryptByPublicKey(inputStr, publicKey);
        System.out.println("加密後：\t"+Base64.encodeBase64String(endcryptData));
        
        //私鑰解密
        byte[] decryptData = RSACoder.decryptByPrivateKey(endcryptData, privateKey);
        String decryptStr = new String(decryptData);
        System.out.println("解密後：\t"+decryptStr);
    }
}