java RSA 加密解密

package com.rsa;

import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
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;

public class Test {

	private static Map<Integer, String> keyMap = new HashMap<Integer, String>();

	public static void main(String[] args) throws Exception {
		// TODO Auto-generated method stub

		// 用于封装随机产生的公钥与私钥
		{ // 生成公钥和私钥
			genKeyPair();
			// 加密字符串
			String message = "df723820";
			System.out.println("随机生成的公钥为:" + keyMap.get(0));
			System.out.println("随机生成的私钥为:" + keyMap.get(1));
			String messageEn = encrypt(message, keyMap.get(0));
			System.out.println(message + "\t加密后的字符串为:" + messageEn);
			String messageDe = decrypt(messageEn, keyMap.get(1));
			System.out.println("还原后的字符串为:" + messageDe);
		}
	}

	public static void genKeyPair() throws NoSuchAlgorithmException { // KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
		// 初始化密钥对生成器，密钥大小为96-1024位
		keyPairGen.initialize(1024, new SecureRandom());
		// 生成一个密钥对，保存在keyPair中
		KeyPair keyPair = keyPairGen.generateKeyPair();
		RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
		// 得到私钥
		RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
		// 得到公钥
		String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
		// 得到私钥字符串
		String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
		// 将公钥和私钥保存到
		keyMap.put(0, publicKeyString);
		// 0表示公钥
		keyMap.put(1, privateKeyString);
		// 1表示私钥
	}

	public static String encrypt(String str, String publicKey) throws Exception {
		// base64编码的公钥
		byte[] decoded = Base64.decodeBase64(publicKey);
		RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA")
				.generatePublic(new X509EncodedKeySpec(decoded));
		// RSA加密
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.ENCRYPT_MODE, pubKey);
		String outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));
		return outStr;
	}

	public static String decrypt(String str, String privateKey) throws Exception {
		// 64位解码加密后的字符串
		byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
		// base64编码的私钥
		byte[] decoded = Base64.decodeBase64(privateKey);
		RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")
				.generatePrivate(new PKCS8EncodedKeySpec(decoded));
		// RSA解密
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, priKey);
		String outStr = new String(cipher.doFinal(inputByte));
		return outStr;
	}

}