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

		// 用於封裝隨機產生的公鑰與私鑰
		{ // 生成公鑰和私鑰
			genKeyPair();
			// 加密字符串
			String message = "df723820";
			System.out.println("隨機生成的公鑰為:" + keyMap.get(0));
			System.out.println("隨機生成的私鑰為:" + keyMap.get(1));
			String messageEn = encrypt(message, keyMap.get(0));
			System.out.println(message + "\t加密后的字符串為:" + messageEn);
			String messageDe = decrypt(messageEn, keyMap.get(1));
			System.out.println("還原后的字符串為:" + messageDe);
		}
	}

	public static void genKeyPair() throws NoSuchAlgorithmException { // KeyPairGenerator類用於生成公鑰和私鑰對，基於RSA算法生成對象
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
		// 初始化密鑰對生成器，密鑰大小為96-1024位
		keyPairGen.initialize(1024, new SecureRandom());
		// 生成一個密鑰對，保存在keyPair中
		KeyPair keyPair = keyPairGen.generateKeyPair();
		RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
		// 得到私鑰
		RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
		// 得到公鑰
		String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
		// 得到私鑰字符串
		String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
		// 將公鑰和私鑰保存到
		keyMap.put(0, publicKeyString);
		// 0表示公鑰
		keyMap.put(1, privateKeyString);
		// 1表示私鑰
	}

	public static String encrypt(String str, String publicKey) throws Exception {
		// base64編碼的公鑰
		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位解碼加密后的字符串
		byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
		// base64編碼的私鑰
		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;
	}

}