BASE64

這其實是一種編解碼方法，但是隻要我們能夠將原文變成肉眼不可識別的內容，其實就是一種加密的方法。

BASE64 的編碼都是按字串長度，以每 3 個 8 bit 的字元為一組，然後針對每組，首先獲取每個字元的 ASCII 編碼，然後將 ASCII 編碼轉換成 8 bit 的二進位制，得到一組 3*8=24 bit 的位元組。然後再將這 24 bit 劃分為 4 個 6 bit 的位元組，並在每個 6 bit 的位元組前面都填兩個高位 0，得到 4 個 8 bit 的位元組，然後將這 4 個 8 bit 的位元組轉換成十進位制，對照 BASE64 編碼表 ，得到對應編碼後的字元。

實現：

/**  
 * Project Name:thread  
 * File Name:Base64Util.java  
 * Package Name:enc.dec  
 * Date:2015年10月21日下午3:49:21  
 * Copyright (c) 2015, [email protected] All Rights Reserved.  
 *  
 */

package enc.dec;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * ClassName:Base64Util <br/>
 * Function: TODO ADD FUNCTION. <br/>
 * Reason: TODO ADD REASON. <br/>
 * Date: 2015年10月21日 下午3:49:21 <br/>
 * 
 * @author chiwei
 * @version
 * @since JDK 1.6
 * @see
 */
public class Base64Util {
	private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
			.toCharArray();

	/**
	 * data[]進行編碼
	 * 
	 * @param data
	 * @return
	 */
	public static String encode(byte[] data) {
		int start = 0;
		int len = data.length;
		StringBuffer buf = new StringBuffer(data.length * 3 / 2);

		int end = len - 3;
		int i = start;
		int n = 0;

		while (i <= end) {
			int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 0x0ff) << 8)
					| (((int) data[i + 2]) & 0x0ff);

			buf.append(legalChars[(d >> 18) & 63]);
			buf.append(legalChars[(d >> 12) & 63]);
			buf.append(legalChars[(d >> 6) & 63]);
			buf.append(legalChars[d & 63]);

			i += 3;

			if (n++ >= 14) {
				n = 0;
				buf.append(" ");
			}
		}

		if (i == start + len - 2) {
			int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 255) << 8);

			buf.append(legalChars[(d >> 18) & 63]);
			buf.append(legalChars[(d >> 12) & 63]);
			buf.append(legalChars[(d >> 6) & 63]);
			buf.append("=");
		} else if (i == start + len - 1) {
			int d = (((int) data[i]) & 0x0ff) << 16;

			buf.append(legalChars[(d >> 18) & 63]);
			buf.append(legalChars[(d >> 12) & 63]);
			buf.append("==");
		}

		return buf.toString();
	}

	public static String encode(String data) {
		try {
			return encode(data.getBytes("UTF-8"));
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	private static int decode(char c) {
		if (c >= 'A' && c <= 'Z')
			return ((int) c) - 65;
		else if (c >= 'a' && c <= 'z')
			return ((int) c) - 97 + 26;
		else if (c >= '0' && c <= '9')
			return ((int) c) - 48 + 26 + 26;
		else
			switch (c) {
			case '+':
				return 62;
			case '/':
				return 63;
			case '=':
				return 0;
			default:
				throw new RuntimeException("unexpected code: " + c);
			}
	}

	/**
	 * Decodes the given Base64 encoded String to a new byte array. The byte
	 * array holding the decoded data is returned.
	 */

	public static byte[] decode(String s) {

		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		try {
			decode(s, bos);
		} catch (IOException e) {
			throw new RuntimeException();
		}
		byte[] decodedBytes = bos.toByteArray();
		try {
			bos.close();
			bos = null;
		} catch (IOException ex) {
			throw new RuntimeException(ex);
		}
		return decodedBytes;
	}

	private static void decode(String s, OutputStream os) throws IOException {
		int i = 0;

		int len = s.length();

		while (true) {
			while (i < len && s.charAt(i) <= ' ')
				i++;

			if (i == len)
				break;

			int tri = (decode(s.charAt(i)) << 18) + (decode(s.charAt(i + 1)) << 12)
					+ (decode(s.charAt(i + 2)) << 6) + (decode(s.charAt(i + 3)));

			os.write((tri >> 16) & 255);
			if (s.charAt(i + 2) == '=')
				break;
			os.write((tri >> 8) & 255);
			if (s.charAt(i + 3) == '=')
				break;
			os.write(tri & 255);

			i += 4;
		}
	}

	/**
	 * data[]進行編碼
	 * 
	 * @param data
	 * @return
	 */
	public static String Base64Encoder(byte[] data) {
		int start = 0;
		int len = data.length;
		StringBuffer buf = new StringBuffer(data.length * 3 / 2);

		int end = len - 3;
		int i = start;
		int n = 0;

		while (i <= end) {
			int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 0x0ff) << 8)
					| (((int) data[i + 2]) & 0x0ff);

			buf.append(legalChars[(d >> 18) & 63]);
			buf.append(legalChars[(d >> 12) & 63]);
			buf.append(legalChars[(d >> 6) & 63]);
			buf.append(legalChars[d & 63]);

			i += 3;

			if (n++ >= 14) {
				// 不需要空格
				n = 0;
			}
		}

		if (i == start + len - 2) {
			int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 255) << 8);

			buf.append(legalChars[(d >> 18) & 63]);
			buf.append(legalChars[(d >> 12) & 63]);
			buf.append(legalChars[(d >> 6) & 63]);
			buf.append("=");
		} else if (i == start + len - 1) {
			int d = (((int) data[i]) & 0x0ff) << 16;

			buf.append(legalChars[(d >> 18) & 63]);
			buf.append(legalChars[(d >> 12) & 63]);
			buf.append("==");
		}

		return buf.toString();
	}

	public static void main(String[] args) {
		System.out.println(encode("tree"));
		System.out.println(new String(decode(encode("tree"))));
	}
}
 

加解密

MD5

Message Digest Algorithm 5
MD5 是用來驗證檔案的一致性的

/**  
 * Project Name:thread  
 * File Name:MD5Util.java  
 * Package Name:enc.dec  
 * Date:2015年10月21日下午3:58:02  
 * Copyright (c) 2015, [email protected] All Rights Reserved.  
 *  
 */

package enc.dec;

import java.security.MessageDigest;

/**
 * ClassName:MD5Util <br/>
 * Function: TODO ADD FUNCTION. <br/>
 * Reason: TODO ADD REASON. <br/>
 * Date: 2015年10月21日 下午3:58:02 <br/>
 * 
 * @author chiwei
 * @version
 * @since JDK 1.6
 * @see
 */
public class MD5Util {

	public static String getMD5(String source) {
		String s = null;
		char hexChar[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D',
				'E', 'F' };
		try {
			MessageDigest md = MessageDigest.getInstance("MD5");
			md.update(source.getBytes());// 使用指定的byte陣列更新摘要
			byte[] hashCalc = md.digest();// 完成雜湊計算
			char result[] = new char[16 * 2];// MD5結果返回的是32位字串，每位是16進製表示的
			int k = 0;
			for (int i = 0; i < 16; i++) {// 迴圈16次，對每個位元組進行操作轉換
				byte everyByte = hashCalc[i];
				result[k++] = hexChar[everyByte >>> 4 & 0xf];// 對每個位元組的高4位進行處理，邏輯右移，再相與
				result[k++] = hexChar[everyByte & 0xf];// 低4位轉換
			}
			s = new String(result);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
		return s;
	}

	public static void main(String[] args) {
		System.out.println(getMD5("tree"));
	}

}
 

SHA

Secure Hash Algorithm

SHA1

SHA-1 有兩個特點：
不可以從訊息摘要中復原資訊
兩個不同的訊息，不會產生同樣的訊息摘要

SHA-1 是一種資料加密演算法，主要是接收一段明文，然後以一種不可逆的方式將它轉換成一段密文，也可以簡單的理解為取一串輸入碼，並把它們轉化為長度較短、位數固定的輸出序列即雜湊值的過程。

對應的還有SHA-256，SHA-512，演算法更加安全

/**  
 * Project Name:thread  
 * File Name:SHAUtil.java  
 * Package Name:enc.dec  
 * Date:2015年10月21日下午4:01:50  
 * Copyright (c) 2015, [email protected] All Rights Reserved.  
 *  
 */

package enc.dec;

import java.security.MessageDigest;

/**
 * ClassName:SHAUtil <br/>
 * Function: TODO ADD FUNCTION. <br/>
 * Reason: TODO ADD REASON. <br/>
 * Date: 2015年10月21日 下午4:01:50 <br/>
 * 
 * @author chiwei
 * @version
 * @since JDK 1.6
 * @see
 */
public class SHAUtil {

	/** 演算法種類 */
	private final static String KEY_SHA1 = "SHA-1";
	private final static String KEY_SHA256 = "SHA-256";
	private final static String KEY_SHA512 = "SHA-512";

	public static String encBySha1(String data) throws Exception {
		// 建立具有指定演算法名稱的資訊摘要
		MessageDigest sha = MessageDigest.getInstance(KEY_SHA1);
		// 使用指定的位元組陣列對摘要進行最後更新
		sha.update(data.getBytes());
		// 完成摘要計算
		byte[] bytes = sha.digest();
		// 將得到的位元組陣列變成字串返回
		return ByteUtil.byteArrayToHexString(bytes);
	}

	public static String encBySha256(String data) throws Exception {
		// 建立具有指定演算法名稱的資訊摘要
		MessageDigest sha = MessageDigest.getInstance(KEY_SHA256);
		// 使用指定的位元組陣列對摘要進行最後更新
		sha.update(data.getBytes());
		// 完成摘要計算
		byte[] bytes = sha.digest();
		// 將得到的位元組陣列變成字串返回
		return ByteUtil.byteArrayToHexString(bytes);
	}

	public static String encBySha512(String data) throws Exception {
		// 建立具有指定演算法名稱的資訊摘要
		MessageDigest sha = MessageDigest.getInstance(KEY_SHA512);
		// 使用指定的位元組陣列對摘要進行最後更新
		sha.update(data.getBytes());
		// 完成摘要計算
		byte[] bytes = sha.digest();
		// 將得到的位元組陣列變成字串返回
		return ByteUtil.byteArrayToHexString(bytes);
	}

	public static void main(String[] args) throws Exception {
		String key = "123";
		System.out.println(encBySha1(key));
		System.out.println(encBySha256(key));
		System.out.println(encBySha512(key));
	}

}

DES,3DES,AES對稱加密

DES 演算法把 64 位的明文輸入塊變為 64 位的密文輸出塊，它所使用的金鑰也是 64 位，其演算法主要分為兩步：

初始置換
其功能是把輸入的 64 位資料塊按位重新組合,並把輸出分為 L0、R0 兩部分，每部分各長 32 位，其置換規則為將輸入的第 58 位換到第一位，第 50 位換到第 2 位 …… 依此類推,最後一位是原來的第 7 位。L0、R0 則是換位輸出後的兩部分，L0 是輸出的左 32 位，R0 是右 32 位，例：設定換前的輸入值為 D1 D2 D3 …… D64，則經過初始置換後的結果為：L0 = D58 D50 …… D8；R0 = D57 D49 …… D7。

逆置換
經過 16 次迭代運算後，得到 L16、R16，將此作為輸入，進行逆置換，逆置換正好是初始置換的逆運算，由此即得到密文輸出。

3DES，也就是“Triple DES”，中文名“三重資料加密演算法”，它相當於是對每個資料塊應用三次 DES 加密演算法。由於計算機運算能力的增強，原版 DES 密碼的金鑰長度變得容易被暴力破解；3DES 即是設計用來提供一種相對簡單的方法，即通過增加 DES 的金鑰長度來避免類似的攻擊，而不是設計一種全新的塊密碼演算法。

AES，全稱為“Advanced Encryption Standard”，中文名“高階加密標準”，在密碼學中又稱 Rijndael 加密法，是美國聯邦政府採用的一種區塊加密標準。AES 加密演算法作為新一代的資料加密標準匯聚了強安全性、高效能、高效率、易用和靈活等優點。AES 設計有三個金鑰長度：128，192，256 位。相對而言，AES 的 128 金鑰比 DES 的 56 金鑰強了 1021 倍。

/**  
 * Project Name:thread  
 * File Name:DESUtil.java  
 * Package Name:enc.dec  
 * Date:2015年10月21日下午4:17:14  
 * Copyright (c) 2015, [email protected] All Rights Reserved.  
 *  
 */

package enc.dec;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.SecretKeySpec;

/**
 * ClassName:DESUtil <br/>
 * Function: TODO ADD FUNCTION. <br/>
 * Reason: TODO ADD REASON. <br/>
 * Date: 2015年10月21日 下午4:17:14 <br/>
 * 
 * @author chiwei
 * @version
 * @since JDK 1.6
 * @see
 */
public class DESUtil {
	private final static String KEY_DES = "DES";
	private static final String KEY_3_DES = "DESede";
	private final static String KEY_AES = "AES"; // 測試
	//長度8位元組
	private final static String DES_KEY = "12345678";
	//長度24位元組
	private final static String DES_3_KEY = "213456781234567812345678";
	//長度16，24，32位元組
	private final static String AES_KEY = "1234567812345678";

	private static byte[] decByDes(byte[] data) throws Exception {
		// DES演算法要求有一個可信任的隨機數源
		SecureRandom random = new SecureRandom();
		DESKeySpec desKey = new DESKeySpec(DES_KEY.getBytes());
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(KEY_DES);
		SecretKey securekey = keyFactory.generateSecret(desKey);
		Cipher cipher = Cipher.getInstance(KEY_DES);
		cipher.init(Cipher.DECRYPT_MODE, securekey, random);
		return cipher.doFinal(data);
	}

	private static byte[] encByDes(byte[] data) throws Exception {
		DESKeySpec desKey = new DESKeySpec(DES_KEY.getBytes());
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(KEY_DES);
		SecretKey securekey = keyFactory.generateSecret(desKey);
		Cipher cipher = Cipher.getInstance(KEY_DES);
		cipher.init(Cipher.ENCRYPT_MODE, securekey);
		return cipher.doFinal(data);
	}

	private static byte[] decBy3Des(byte[] data) throws Exception {
		SecureRandom random = new SecureRandom();
		SecretKey deskey = new SecretKeySpec(DES_3_KEY.getBytes(), KEY_3_DES);
		Cipher cipher = Cipher.getInstance(KEY_3_DES);
		cipher.init(Cipher.DECRYPT_MODE, deskey, random);
		return cipher.doFinal(data);
	}

	private static byte[] encBy3Des(byte[] data) throws Exception {
		SecureRandom random = new SecureRandom();
		SecretKey deskey = new SecretKeySpec(DES_3_KEY.getBytes(), KEY_3_DES);
		Cipher cipher = Cipher.getInstance(KEY_3_DES);
		cipher.init(Cipher.ENCRYPT_MODE, deskey, random);
		return cipher.doFinal(data);
	}

	private static byte[] decByAes(byte[] data) throws Exception {
		SecretKey deskey = new SecretKeySpec(AES_KEY.getBytes(), KEY_AES);
		Cipher cipher = Cipher.getInstance(KEY_AES);
		cipher.init(Cipher.DECRYPT_MODE, deskey);
		return cipher.doFinal(data);
	}

	private static byte[] encByAes(byte[] data) throws Exception {
		SecretKey deskey = new SecretKeySpec(AES_KEY.getBytes(), KEY_AES);
		Cipher cipher = Cipher.getInstance(KEY_AES);
		cipher.init(Cipher.ENCRYPT_MODE, deskey);
		return cipher.doFinal(data);
	}

	public static void main(String[] args) throws Exception {
		System.out.println("DES金鑰:\n" + DES_KEY);
		System.out.println("DES金鑰位元組長度:\n" + DES_KEY.getBytes().length);
		String word = "123";
		System.out.println("原文：" + word);
		System.out.println("=============DES=============");
		byte b[] = encByDes(word.getBytes());
		String encWord = new String(b);
		System.out.println("加密後：" + encWord);
		System.out.println("解密後：" + new String(decByDes(b)));
		System.out.println("=============3DES=============");
		System.out.println("3DES金鑰:" + DES_3_KEY);
		System.out.println("3DES金鑰位元組長度:" + DES_3_KEY.getBytes().length);
		b = encBy3Des(word.getBytes());
		encWord = new String(b);
		System.out.println("加密後：" + encWord);
		System.out.println("解密後：" + new String(decBy3Des(b)));
		System.out.println("=============AES=============");
		System.out.println("AES金鑰:" + AES_KEY);
		System.out.println("AES金鑰位元組長度:" + AES_KEY.getBytes().length);
		b = encByAes(word.getBytes());
		encWord = new String(b);
		System.out.println("加密後：" + encWord);
		System.out.println("解密後：" + new String(decByAes(b)));
	}

}

RSA非對稱加密

/**  
 * Project Name:thread  
 * File Name:RSAUtil.java  
 * Package Name:enc.dec  
 * Date:2015年10月22日上午9:21:01  
 * Copyright (c) 2015, [email protected] All Rights Reserved.  
 *  
 */

package enc.dec;

import java.io.ByteArrayOutputStream;
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.Signature;
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 com.alibaba.fastjson.JSONObject;

/**
 * ClassName:RSAUtil <br/>
 * Function: TODO ADD FUNCTION. <br/>
 * Reason: TODO ADD REASON. <br/>
 * Date: 2015年10月22日 上午9:21:01 <br/>
 * 
 * @author chiwei
 * @version
 * @since JDK 1.6
 * @see
 */
public class RSAUtil {

	/**
	 * 加密演算法RSA
	 */
	public static final String KEY_ALGORITHM = "RSA";

	/**
	 * 簽名演算法
	 */
	public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

	/**
	 * 獲取公鑰的key
	 */
	private static final String PUBLIC_KEY = "RSAPublicKey";

	private static final int keyLen = 512;// 金鑰長度

	/**
	 * 獲取私鑰的key
	 */
	private static final String PRIVATE_KEY = "RSAPrivateKey";

	/**
	 * RSA最大加密明文大小
	 */
	private static final int MAX_ENCRYPT_BLOCK = keyLen / 8 - 11;

	/**
	 * RSA最大解密密文大小
	 */
	private static final int MAX_DECRYPT_BLOCK = keyLen / 8;

	/**
	 * 
	 * genKeyPair:(). <br/>  
	  
	 *  生成公司鑰對，返回的是經過BASE64編碼的金鑰
	 * @author chiwei  
	 * @return
	 * @throws Exception  
	 * @since JDK 1.6
	 */
	public static Map<String, Object> genKeyPair() throws Exception {
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
		keyPairGen.initialize(keyLen);
		KeyPair keyPair = keyPairGen.generateKeyPair();
		RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
		RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
		Map<String, Object> keyMap = new HashMap<String, Object>(2);
		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);
		return keyMap;
	}

	/**
	 * 
	 * sign:(). <br/>  
	  
	 *  用私鑰進行簽名，返回BASE64編碼的內容
	 * @author chiwei  
	 * @param data
	 * @param privateKey
	 * @return
	 * @throws Exception  
	 * @since JDK 1.6
	 */
	public static String sign(byte[] data, String privateKey) throws Exception {
		byte[] keyBytes = Base64Util.decode(privateKey);
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
		Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
		signature.initSign(privateK);
		signature.update(data);
		return Base64Util.encode(signature.sign());
	}

	/**
	 * 
	 * verify:(). <br/>  
	  
	 *  用公鑰對簽名進行驗證
	 * @author chiwei  
	 * @param data
	 * @param publicKey
	 * @param sign
	 * @return
	 * @throws Exception  
	 * @since JDK 1.6
	 */
	public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {
		byte[] keyBytes = Base64Util.decode(publicKey);
		X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		PublicKey publicK = keyFactory.generatePublic(keySpec);
		Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
		signature.initVerify(publicK);
		signature.update(data);
		return signature.verify(Base64Util.decode(sign));
	}

	/**
	 * 
	 * decryptByPrivateKey:(). <br/>  
	  
	 *  私鑰解密
	 * @author chiwei  
	 * @param encryptedData
	 * @param privateKey
	 * @return
	 * @throws Exception  
	 * @since JDK 1.6
	 */
	public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey)
			throws Exception {
		byte[] keyBytes = Base64Util.decode(privateKey);
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.DECRYPT_MODE, privateK);
		int inputLen = encryptedData.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 對資料分段解密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
				cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_DECRYPT_BLOCK;
		}
		byte[] decryptedData = out.toByteArray();
		out.close();
		return decryptedData;
	}

	/**
	 * 
	 * decryptByPublicKey:(). <br/>  
	  
	 *  公鑰解密
	 * @author chiwei  
	 * @param encryptedData
	 * @param publicKey
	 * @return
	 * @throws Exception  
	 * @since JDK 1.6
	 */
	public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey)
			throws Exception {
		byte[] keyBytes = Base64Util.decode(publicKey);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key publicK = keyFactory.generatePublic(x509KeySpec);
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.DECRYPT_MODE, publicK);
		int inputLen = encryptedData.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 對資料分段解密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
				cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_DECRYPT_BLOCK;
		}
		byte[] decryptedData = out.toByteArray();
		out.close();
		return decryptedData;
	}

	/**
	 * 
	 * encryptByPublicKey:(). <br/>  
	  
	 *  公鑰加密
	 * @author chiwei  
	 * @param data
	 * @param publicKey
	 * @return
	 * @throws Exception  
	 * @since JDK 1.6
	 */
	public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {
		byte[] keyBytes = Base64Util.decode(publicKey);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key publicK = keyFactory.generatePublic(x509KeySpec);
		// 對資料加密
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.ENCRYPT_MODE, publicK);
		int inputLen = data.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 對資料分段加密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
				cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(data, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_ENCRYPT_BLOCK;
		}
		byte[] encryptedData = out.toByteArray();
		out.close();
		return encryptedData;
	}

	/**
	 * 
	 * encryptByPrivateKey:(). <br/>  
	  
	 *  私鑰加密
	 * @author chiwei  
	 * @param data
	 * @param privateKey
	 * @return
	 * @throws Exception  
	 * @since JDK 1.6
	 */
	public static byte[] encryptByPrivateKey(byte[] data, String privateKey) throws Exception {
		byte[] keyBytes = Base64Util.decode(privateKey);
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
		Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
		cipher.init(Cipher.ENCRYPT_MODE, privateK);
		int inputLen = data.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 對資料分段加密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
				cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(data, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_ENCRYPT_BLOCK;
		}
		byte[] encryptedData = out.toByteArray();
		out.close();
		return encryptedData;
	}

	/**
	 * 
	 * getPrivateKey:(). <br/>  
	  
	 *  獲取BASE64編碼的私鑰
	 * @author chiwei  
	 * @param keyMap
	 * @return
	 * @throws Exception  
	 * @since JDK 1.6
	 */
	public static String getPrivateKey(Map<String, Object> keyMap) throws Exception {
		Key key = (Key) keyMap.get(PRIVATE_KEY);
		return Base64Util.encode(key.getEncoded());
	}

	/**
	 * 
	 * getPublicKey:(). <br/>  
	  
	 *  獲取BASE64編碼的公鑰
	 * @author chiwei  
	 * @param keyMap
	 * @return
	 * @throws Exception  
	 * @since JDK 1.6
	 */
	public static String getPublicKey(Map<String, Object> keyMap) throws Exception {
		Key key = (Key) keyMap.get(PUBLIC_KEY);
		return Base64Util.encode(key.getEncoded());
	}

	public static void main(String args[]) {
		JSONObject json = new JSONObject();
		json.put("deviceId", "1");
		json.put("clientVersion", "2");
		json.put("platform", "1");
		JSONObject position = new JSONObject();
		position.put("location_latitude_key", "10.98");
		position.put("location_longtitude_key", "110.98");
		json.put("position", position);
		json.put("city", "杭州市");
		json.put("locatedAddress", "");
		json.put("romVersion", "1");
		json.put("commandId", 0x125);
		json.put("userId", 10049);
		json.put("orderId", 10053);
		System.out.println(json);
		String publicKey = "MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAIc7AHO19/BdTKI18QDeqOxHCNHI w8+2C15kvE5h+kYoQxCq3IdVDsJJKFJSAtfOe7WHgLUDOpAZaHcUnpW7HpUC AwEAAQ==";// "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCZozfHvyz7LZIAo7BPX2HE DHc4CZR9UIwPC/omfaJ62f8l2na+YRKQHBE220+RQfqupVMKmy7QYo+hAjs4 MqCgCedqyWBwHhrhTbQp5FuZ/xaqFCuz/ntyYzz7NrYoD3ijtwBXUrx6kTJf xtkB/Nhd317JHuzxPR9bNUj3K5pLfwIDAQAB";
		String privateKey = "MIIBUwIBADANBgkqhkiG9w0BAQEFAASCAT0wggE5AgEAAkEAhzsAc7X38F1M ojXxAN6o7EcI0cjDz7YLXmS8TmH6RihDEKrch1UOwkkoUlIC1857tYeAtQM6 kBlodxSelbselQIDAQABAkBwhC4XGMPoMajumpUhFSJWHbB/5FzQOXbyHjzz tt/neKONwuB25QJ+DehwtKGnjDtcrSlUbNYIc0L95eKPGvJBAiEA39pNrReU WThfcQkz1TEmL+Pqh09Uf5KdkUJFRn3rEsUCIQCapplvyKoWiC2//J8NXUds 1SyNv5+vsXlwhtPqJsNZkQIgEEIy0hecVr6ZcARTF3DybRgIuLsyT/G+MAa4 MV6D7GECICocr6+G3vofvwWGjvEes3JpYiZ/Rcab90uzC0W5pHxhAiAvPq16 AvszXkXVZXgvEHoyG2qvbj0I7VkCsHI8C0E1xQ==";// "MIICdQIBADANBgkqhkiG9w0BAQEFAASCAl8wggJbAgEAAoGBAJmjN8e/LPst kgCjsE9fYcQMdzgJlH1QjA8L+iZ9onrZ/yXadr5hEpAcETbbT5FB+q6lUwqb LtBij6ECOzgyoKAJ52rJYHAeGuFNtCnkW5n/FqoUK7P+e3JjPPs2tigPeKO3 AFdSvHqRMl/G2QH82F3fXske7PE9H1s1SPcrmkt/AgMBAAECf0sEZzghINWE asXlJzGaYSJY891o0BhgPAMc1gf1UGCsEOlqwpAy1d2H1t/yNee3T6/3CZUk MLePaJI1hLTsA4FcGzEWKUy7Hn2CqIjUzkJdax6CYXlK0hcoI47fiCr7Wtcx U/6P1uN+shA5ICHF0nZYJ2vEO1Vw/xMVGnLIRykCQQDwHJ0yOJZde7nZxo56 xka2C1tfMNjziXkdFH6EGfaiT0iJkJ+Kd11m0LukUxLPo5U1O63ZYkWOtFen wL2FmJTzAkEAo83FAO23KDZAyaPJg4K1PWqScF8+BDK51QxmJR0iCcl2umck jTfnO53wE8zjGNH/nqKQK6D+RUs8vEWaI37CRQJBAKKEW4mQb4XappJWKD3F UjsJONEXOOCtncInCvLSt/JoA0rJDpMj854Rjc/NQqAzslwThrnqH/ZU7jdm 52AzRC0CQB62djm2WKExivRDwYTm/RSG5u4q7XXcDPvlV0GeNMOhAqHwtOnF kZWcB2evAuWkeklEMcP8a7CSatDiPARrwAECQQC0SMsT/xukGzOh4SkHEirN bdFwdLdFeJf+8O3Tsf7iYlTNhnGEgTLQeaf3xOoivGtJEXZwT7vJWtiTUXRW 8P1v";
		try {
			// Map key = genKeyPair();
			// publicKey = getPublicKey(key);
			// privateKey = getPrivateKey(key);
			System.out.println("公鑰-->" + publicKey);
			System.out.println("私鑰-->" + privateKey);
			System.out.println("待加密的字串：" + json);
			byte[] enBy = encryptByPublicKey(json.toJSONString().getBytes(), publicKey);
			String enStr = new String(enBy, "UTF-8");
			System.out.println("加密後：" + enStr);
			String enEncode = Base64Util.encode(enBy);
			System.out.println("加密後編碼內容：" + enEncode);
			byte[] deBy = decryptByPrivateKey(Base64Util.decode(enEncode), privateKey);
			System.out.println("解密後：" + new String(deBy));
			System.out.println("解密後編碼內容：" + Base64Util.encode(deBy));
			String sign = sign(enBy,privateKey);
			System.out.println("簽名："+sign);
			System.out.println("對簽名驗證："+verify(enBy, publicKey, sign));
			System.out.println("BASE64編碼密文摘要："+MD5Util.getMD5(enEncode));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

資料加密：

為了保證資料的安全性，不會洩露資料的真是內容

資料摘要：

為了確保資料中途沒有被篡改過，資料的內容時完整的正確的

資料簽名：

為了保證資料是對方過來的，而不是從別的地方來的

在真實的網際網路應用中，加密場景非常重要

1、對資料加密

2、對密文生成摘要

3、對摘要進行簽名

4、將密文和簽名一起傳送

這樣就保證了資料的安全性

這裡還有一個唯一的漏洞就是接收方的公鑰被人替換了，所以就出現了證書認證中心

確保公鑰的安全性，在傳送資料的時候加上數字證書。