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AJAXJS aims to full-stack, not only the server-side framework, but also integrates the front-end library. It's written in HTML5 + Java, a successor to the JVM platform, efficient, secure, stable, cross-platform and many other advantages, but it abandoned the traditional enterprise architecture brought about by the large and bloated, emphasizing the lightweight, and fast, very suitable for the Internet fast application.

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/**
 * Copyright 2015 Sp42 [email protected]
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.ajaxjs.util.cryptography;

import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

/**
 * RSA 非对称加密/解密
 * 
 * @author Sp42 [email protected]
 *
 */
public class RSA {
	public static final String KEY_ALGORITHM = "RSA";
	/** 貌似默认是RSA/NONE/PKCS1Padding，未验证 */
	public static final String CIPHER_ALGORITHM = "RSA/ECB/PKCS1Padding";
	public static final String PUBLIC_KEY = "publicKey";
	public static final String PRIVATE_KEY = "privateKey";

	/** RSA密钥长度必须是64的倍数，在512~65536之间。默认是1024 */
	public static final int KEY_SIZE = 2048;

	/**
	 * 生成密钥对。注意这里是生成密钥对KeyPair，再由密钥对获取公私钥
	 * 
	 * @return 密钥对
	 */
	public static Map generateKeyBytes() {
		KeyPairGenerator keyPairGenerator;

		try {
			keyPairGenerator = KeyPairGenerator.getInstance(KEY_ALGORITHM);
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
			return null;
		}

		keyPairGenerator.initialize(KEY_SIZE);
		KeyPair keyPair = keyPairGenerator.generateKeyPair();
		RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
		RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

		Map keyMap = new HashMap<>();
		keyMap.put(PUBLIC_KEY, publicKey.getEncoded());
		keyMap.put(PRIVATE_KEY, privateKey.getEncoded());

		return keyMap;
	}

	/**
	 * 还原公钥，X509EncodedKeySpec 用于构建公钥的规范
	 * 
	 * @param keyBytes 公钥字节码
	 * @return 公钥
	 */
	public static PublicKey restorePublicKey(byte[] keyBytes) {
		X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(keyBytes);

		try {
			KeyFactory factory = KeyFactory.getInstance(KEY_ALGORITHM);
			return factory.generatePublic(x509EncodedKeySpec);
		} catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
			e.printStackTrace();
			return null;
		}
	}

	/**
	 * 还原私钥，PKCS8EncodedKeySpec 用于构建私钥的规范
	 * 
	 * @param keyBytes 私钥字节码
	 * @return 私钥
	 */
	public static PrivateKey restorePrivateKey(byte[] keyBytes) {
		PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(keyBytes);

		try {
			KeyFactory factory = KeyFactory.getInstance(KEY_ALGORITHM);
			return factory.generatePrivate(pkcs8EncodedKeySpec);
		} catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
			e.printStackTrace();
			return null;
		}
	}

	/**
	 * 加密，三步走。
	 * 
	 * @param key       密钥
	 * @param plainText 加密的内容
	 * @return 结果
	 */
	public static byte[] RSAEncode(PublicKey key, byte[] plainText) {
		try {
			Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
			cipher.init(Cipher.ENCRYPT_MODE, key);
			return cipher.doFinal(plainText);
		} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException
				| BadPaddingException e) {
			e.printStackTrace();
			return null;
		}
	}

	/**
	 * 解密，三步走。
	 * 
	 * @param key         密钥
	 * @param encodedText 解密的内容
	 * @return 解密结果
	 */
	public static String RSADecode(PrivateKey key, byte[] encodedText) {
		try {
			Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
			cipher.init(Cipher.DECRYPT_MODE, key);
			return new String(cipher.doFinal(encodedText));
		} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException
				| BadPaddingException e) {
			e.printStackTrace();
			return null;
		}
	}
}