RSA加密算法介绍

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什么是RSA

RSA是一种加密方式，RSA加密算法是一种非对称加密算法。

非对称，是指在加密和解密时使用不同的密钥。RSA算法中，加密密钥publicKey(公钥)是公开的,解密密钥secretKey(私钥)由使用者保存。

使用

加入lib

commons-codec-1.15.jar

RSAEncrypt.java

import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.security.*;
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;

public class RSAEncrypt {

	//用于封装随机产生的公钥与私钥
	private static Map<Integer, String> keyMap = new HashMap<Integer, String>();


	// 私钥
	private static final String PUBLIC_KEY = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCQD6YnXZiHj/5tl2sPf2i4mzcraFzaCs21SuqPe/G0gfHe1iHyBBrhuaE2t6v3CEkQ3/b2Srop7E6hHp0tWeZrKPxsNGvla9S9C4PFK2cCHoFh0cT3JjnDeITc/ufCC6UPK+JuRwiqrwVSutd5sQXjU0v3gqNgleRWvV+bayaxeQIDAQAB";
	// 公钥
	private static final String PRIVATE_KEY ="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";

	public static void main(String[] args) throws Exception {
		//生成公钥和私钥
		genKeyPair();
		//加密字符串
		String message = "ABC123abc一二三";
		System.out.println("加密前的字符串："+ message);
//		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));
		System.out.println("公钥为:" + PUBLIC_KEY);
		System.out.println("私钥为:" + PRIVATE_KEY);
		String messageEn = encrypt(message,PUBLIC_KEY);
		System.out.println("加密后的字符串为:" + messageEn);
		String messageDe = decrypt(messageEn,PRIVATE_KEY);
		System.out.println("解密后的字符串为:" + messageDe);
	}

	/**
	 * 随机生成密钥对
	 * @throws NoSuchAlgorithmException
	 */
	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Map
		keyMap.put(0,publicKeyString);  //0表示公钥
		keyMap.put(1,privateKeyString);  //1表示私钥
	}
	/**
	 * RSA公钥加密
	 *
	 * @param str
	 *            加密字符串
	 * @param publicKey
	 *            公钥
	 * @return 密文
	 * @throws Exception
	 *             加密过程中的异常信息
	 */
	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;
	}

	/**
	 * RSA私钥解密
	 *
	 * @param str
	 *            加密字符串
	 * @param privateKey
	 *            私钥
	 * @return 铭文
	 * @throws Exception
	 *             解密过程中的异常信息
	 */
	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;
	}
}