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java 常用工具类,作为 apache-commons的补充
There is a newer version: 5.3.2302
package com.centit.support.security;

import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

import org.apache.commons.net.util.Base64;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;

import sun.security.rsa.RSAPrivateCrtKeyImpl;
import sun.security.rsa.RSAPublicKeyImpl;

@SuppressWarnings("unused")
public abstract class RSASecurityUtils {
	/** 指定加密算法为RSA */
	private static final String ALGORITHM = "RSA";
	/** 密钥长度，用来初始化 
	 * 加密字符串长度受秘钥长度的限制
	 * 当KEYSIZE为1024时最多加密117个字节，长度为2048时可以加密245个字节*/
	private static final int KEYSIZE = 1024;

	public static KeyPair generateKeyPair() throws Exception {
		return generateKeyPair(KEYSIZE);
	}	
	/**
	 * 生成密钥对
	 * @param  keysize 密码大小
	 * @return  密钥对
	 * @throws Exception 父类抛出的异常
	 */
	public static KeyPair generateKeyPair(int keysize) throws Exception {

		// /** RSA算法要求有一个可信任的随机数源 */
		// SecureRandom secureRandom = new SecureRandom();

		/** 为RSA算法创建一个KeyPairGenerator对象 */
		KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);

		/** 利用上面的随机数据源初始化这个KeyPairGenerator对象 */
		// keyPairGenerator.initialize(KEYSIZE, secureRandom);
		keyPairGenerator.initialize(keysize);

		/** 生成密匙对 */
		KeyPair keyPair = keyPairGenerator.generateKeyPair();
		return keyPair;
	}

	/**
	 * 加密方法
	 * @param source
	 *            源数据  加密字符串长度受秘钥长度的限制，最多加密245个字节
	 * @param key 密码
	 * @return 密文
	 * @throws Exception 父类抛出的异常
	 */
	public static String encrypt(String source,Key key) throws Exception {
		generateKeyPair();
		Key publicKey = key;
		
		/** 得到Cipher对象来实现对源数据的RSA加密 */
		Cipher cipher = Cipher.getInstance(ALGORITHM);
		cipher.init(Cipher.ENCRYPT_MODE, publicKey);
		byte[] b = source.getBytes();
		/** 执行加密操作 */
		byte[] b1 = cipher.doFinal(b);
		//BASE64Encoder encoder = new BASE64Encoder();
		return Base64.encodeBase64String(b1);
	}

	/**
	 * 解密算法
	 * 
	 * @param cryptograph
	 *            密文
	 * @param key 密码
     * @return 密文
	 * @throws Exception 父类抛出的异常
	 */
	public static String decrypt(String cryptograph,Key key) throws Exception {
		Key privateKey = key;
		/** 得到Cipher对象对已用公钥加密的数据进行RSA解密 */
		Cipher cipher = Cipher.getInstance(ALGORITHM);
		cipher.init(Cipher.DECRYPT_MODE, privateKey);
		//BASE64Decoder decoder = new BASE64Decoder();
		byte[] b1 = Base64.decodeBase64(cryptograph);

		/** 执行解密操作 */
		byte[] b = cipher.doFinal(b1);
		return new String(b);
	}

	public static String keyPairToJson(KeyPair keyPair) {
		Map keyJson = new HashMap();
		keyJson.put("private", Base64.encodeBase64String(keyPair.getPrivate().getEncoded()));
		keyJson.put("public", Base64.encodeBase64String(keyPair.getPublic().getEncoded()));
		return JSON.toJSONString(keyJson);
	}
	
	public static KeyPair keyPairFromJson(String keyJsonString) throws InvalidKeyException{		
		JSONObject keyJson =  (JSONObject) JSON.parseObject(keyJsonString);
		return new KeyPair(
				new RSAPublicKeyImpl(Base64.decodeBase64(keyJson.getString("public"))),
				RSAPrivateCrtKeyImpl.newKey(
						Base64.decodeBase64(keyJson.getString("private"))));
	}
	
}