JAVA RSA加密公私钥

RSA加密算法：RSA加密算法是一种非对称加密算法。解密者拥有私钥，并且将由私钥计算生成的公钥发布给加密者。加密都使用公钥进行加密，并将密文发送到解密者，解密者用私钥解密将密文解码为明文。

import org.apache.commons.codec.binary.Base64;
import javax.crypto.Cipher;

import java.math.BigInteger;
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.RSAPrivateKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

public class RSAEncrypt {
	private static Map<String, String> keyMap = new HashMap<String, String>();  //用于封装随机产生的公钥与私钥
	private static Map<String, BigInteger> modMap = new HashMap<>();
	public static void main(String[] args) throws Exception {
		//生成公钥和私钥
		genKeyPair();
		//加密字符串
		String message = "license";
		System.out.println("随机生成的公钥为:" + keyMap.get("publicKeyString"));
		System.out.println("随机生成的私钥为:" + keyMap.get("privateKeyString"));
		String messageEn = encrypt(message,keyMap.get("publicKeyString"));//公钥加密
		System.out.println(message + "\t加密后的字符串为:" + messageEn);
		String messageDe = decrypt(messageEn,keyMap.get("privateKeyString"));//私钥解密
		System.out.println("decrypt还原后的字符串为:" + messageDe);
		String messageDeMod = decryptMod(messageEn,modMap.get("privateMod"), modMap.get("privatePub"));
		System.out.println("decryptMod还原后的字符串为:" + messageDeMod);
		String messageDeModStr = decryptModStr(messageEn,keyMap.get("privateModStr"), keyMap.get("privatePubStr"));
		System.out.println("decryptModStr还原后的字符串为:" + messageDeModStr);
	}

	/**
	 * 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("publicKeyString",publicKeyString);
		keyMap.put("privateKeyString",privateKeyString);  

		String publicModStr = new String(Base64.encodeBase64((publicKey.getModulus().toByteArray())));
		String publicPubStr = new String(Base64.encodeBase64((publicKey.getPublicExponent().toByteArray())));
		String privateModStr = new String(Base64.encodeBase64((privateKey.getModulus().toByteArray())));
		String privatePubStr = new String(Base64.encodeBase64((privateKey.getPrivateExponent().toByteArray())));
		keyMap.put("publicModStr",publicModStr);
		keyMap.put("publicPubStr",publicPubStr);
		keyMap.put("privateModStr",privateModStr);
		keyMap.put("privatePubStr",privatePubStr); 

		modMap.put("publicMod", publicKey.getModulus());
		modMap.put("publicPub", publicKey.getPublicExponent());
		modMap.put("privateMod", privateKey.getModulus());
		modMap.put("privatePub", privateKey.getPrivateExponent());

		System.out.println("publicModStr:"+publicModStr);
		System.out.println("publicPubStr:"+publicPubStr);
		System.out.println("publicMod:"+publicKey.getModulus());
		System.out.println("publicPub:"+publicKey.getPublicExponent());
		System.out.println("privateModStr:"+privateModStr);
		System.out.println("privatePubStr:"+privatePubStr);
		System.out.println("privateMod:"+privateKey.getModulus());
		System.out.println("privatePub:"+privateKey.getPrivateExponent());
	}
	/**
	 * 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;
	}

	/**
	 * 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 decryptMod(String str, BigInteger privateMod, BigInteger privatePub) throws Exception{
		//64位解码加密后的字符串
		byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));

		RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(privateMod, privatePub);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(priKeySpec);
		//RSA解密
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, priKey);
		String outStr = new String(cipher.doFinal(inputByte));
		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 decryptModStr(String str, String privateModStr, String privatePubStr) throws Exception{
		//64位解码加密后的字符串
		byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));

		BigInteger privateMod = new BigInteger(Base64.decodeBase64(privateModStr));
		BigInteger privatePub = new BigInteger(Base64.decodeBase64(privatePubStr));
		RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(privateMod, privatePub);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(priKeySpec);
		//RSA解密
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, priKey);
		String outStr = new String(cipher.doFinal(inputByte));
		return outStr;
	}

}

原文地址：https://www.cnblogs.com/RealWorld/p/12559259.html