Maven依赖

    <dependency>
      <groupId>cn.hutool</groupId>
      <artifactId>hutool-all</artifactId>
      <version>5.8.31</version>
    </dependency>

RSA 非对称加密工具类

import cn.hutool.core.codec.Base64;
import cn.hutool.core.util.StrUtil;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.*;
import java.util.HashMap;
import java.util.Map;

/**
 * <p>IJPay 让支付触手可及，封装了微信支付、支付宝支付、银联支付常用的支付方式以及各种常用的接口。</p>
 *
 * <p>不依赖任何第三方 mvc 框架，仅仅作为工具使用简单快速完成支付模块的开发，可轻松嵌入到任何系统里。 </p>
 *
 * <p>IJPay 交流群: 723992875、864988890</p>
 *
 * <p>Node.js 版: <a href="https://gitee.com/javen205/TNWX">https://gitee.com/javen205/TNWX</a></p>
 *
 * <p>RSA 非对称加密工具类</p>
 *
 * @author Javen
 */
public class RsaKit {

	/**
	 * RSA最大加密明文大小
	 */
	private static final int MAX_ENCRYPT_BLOCK = 117;

	/**
	 * RSA最大解密密文大小
	 */
	private static final int MAX_DECRYPT_BLOCK = 128;

	/**
	 * 加密算法RSA
	 */
	private static final String KEY_ALGORITHM = "RSA";

	/**
	 * 生成公钥和私钥
	 *
	 * @throws Exception 异常信息
	 */
	public static Map<String, String> getKeys() throws Exception {
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
		keyPairGen.initialize(1024);
		KeyPair keyPair = keyPairGen.generateKeyPair();
		RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
		RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

		String publicKeyStr = getPublicKeyStr(publicKey);
		String privateKeyStr = getPrivateKeyStr(privateKey);

		Map<String, String> map = new HashMap<String, String>(2);
		map.put("publicKey", publicKeyStr);
		map.put("privateKey", privateKeyStr);

		System.out.println("公钥\r\n" + publicKeyStr);
		System.out.println("私钥\r\n" + privateKeyStr);
		return map;
	}

	/**
	 * 使用模和指数生成RSA公钥
	 * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA
	 * /None/NoPadding】
	 *
	 * @param modulus  模
	 * @param exponent 公钥指数
	 * @return {@link RSAPublicKey}
	 */
	public static RSAPublicKey getPublicKey(String modulus, String exponent) {
		try {
			BigInteger b1 = new BigInteger(modulus);
			BigInteger b2 = new BigInteger(exponent);
			KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
			RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2);
			return (RSAPublicKey) keyFactory.generatePublic(keySpec);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}

	/**
	 * 使用模和指数生成RSA私钥
	 * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA
	 * /None/NoPadding】
	 *
	 * @param modulus  模
	 * @param exponent 指数
	 * @return {@link RSAPrivateKey}
	 */
	public static RSAPrivateKey getPrivateKey(String modulus, String exponent) {
		try {
			BigInteger b1 = new BigInteger(modulus);
			BigInteger b2 = new BigInteger(exponent);
			KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
			RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(b1, b2);
			return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}

	/**
	 * 公钥加密
	 *
	 * @param data      需要加密的数据
	 * @param publicKey 公钥
	 * @return 加密后的数据
	 * @throws Exception 异常信息
	 */
	public static String encryptByPublicKey(String data, String publicKey) throws Exception {
		return encryptByPublicKey(data, publicKey, "RSA/ECB/PKCS1Padding");
	}

	/**
	 * 公钥加密
	 *
	 * @param data      需要加密的数据
	 * @param publicKey 公钥
	 * @return 加密后的数据
	 * @throws Exception 异常信息
	 */
	public static String encryptByPublicKeyByWx(String data, String publicKey) throws Exception {
		return encryptByPublicKey(data, publicKey, "RSA/ECB/OAEPWITHSHA-1ANDMGF1PADDING");
	}

	/**
	 * 公钥加密
	 *
	 * @param data      需要加密的数据
	 * @param publicKey 公钥
	 * @param fillMode  填充模式
	 * @return 加密后的数据
	 * @throws Exception 异常信息
	 */
	public static String encryptByPublicKey(String data, String publicKey, String fillMode) throws Exception {
		byte[] dataByte = data.getBytes(StandardCharsets.UTF_8);
		byte[] keyBytes = Base64.decode(publicKey);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key key = keyFactory.generatePublic(x509KeySpec);
		// 对数据加密
		Cipher cipher = Cipher.getInstance(fillMode);
		cipher.init(Cipher.ENCRYPT_MODE, key);
		int inputLen = dataByte.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 对数据分段加密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
				cache = cipher.doFinal(dataByte, offSet, MAX_ENCRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(dataByte, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_ENCRYPT_BLOCK;
		}
		byte[] encryptedData = out.toByteArray();
		out.close();
		return StrUtil.str(Base64.encode(encryptedData));
	}

	/**
	 * 私钥签名
	 *
	 * @param data       需要加密的数据
	 * @param privateKey 私钥
	 * @return 加密后的数据
	 * @throws Exception 异常信息
	 */
	public static String encryptByPrivateKey(String data, String privateKey) throws Exception {
		PKCS8EncodedKeySpec priPkcs8 = new PKCS8EncodedKeySpec(Base64.decode(privateKey));
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		PrivateKey priKey = keyFactory.generatePrivate(priPkcs8);
		java.security.Signature signature = java.security.Signature.getInstance("SHA256WithRSA");

		signature.initSign(priKey);
		signature.update(data.getBytes(StandardCharsets.UTF_8));
		byte[] signed = signature.sign();
		return StrUtil.str(Base64.encode(signed));
	}

	/**
	 * 私钥签名
	 *
	 * @param data       需要加密的数据
	 * @param privateKey 私钥
	 * @return 加密后的数据
	 * @throws Exception 异常信息
	 */
	public static String encryptByPrivateKey(String data, PrivateKey privateKey) throws Exception {
		java.security.Signature signature = java.security.Signature.getInstance("SHA256WithRSA");
		signature.initSign(privateKey);
		signature.update(data.getBytes(StandardCharsets.UTF_8));
		byte[] signed = signature.sign();
		return StrUtil.str(Base64.encode(signed));
	}

	/**
	 * 公钥验证签名
	 *
	 * @param data      需要加密的数据
	 * @param sign      签名
	 * @param publicKey 公钥
	 * @return 验证结果
	 * @throws Exception 异常信息
	 */
	public static boolean checkByPublicKey(String data, String sign, String publicKey) throws Exception {
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		byte[] encodedKey = Base64.decode(publicKey);
		PublicKey pubKey = keyFactory.generatePublic(new X509EncodedKeySpec(encodedKey));
		java.security.Signature signature = java.security.Signature.getInstance("SHA256WithRSA");
		signature.initVerify(pubKey);
		signature.update(data.getBytes(StandardCharsets.UTF_8));
		return signature.verify(Base64.decode(sign.getBytes(StandardCharsets.UTF_8)));
	}

	/**
	 * 公钥验证签名
	 *
	 * @param data      需要加密的数据
	 * @param sign      签名
	 * @param publicKey 公钥
	 * @return 验证结果
	 * @throws Exception 异常信息
	 */
	public static boolean checkByPublicKey(String data, String sign, PublicKey publicKey) throws Exception {
		java.security.Signature signature = java.security.Signature.getInstance("SHA256WithRSA");
		signature.initVerify(publicKey);
		signature.update(data.getBytes(StandardCharsets.UTF_8));
		return signature.verify(Base64.decode(sign.getBytes(StandardCharsets.UTF_8)));
	}

	/**
	 * 私钥解密
	 *
	 * @param data       需要解密的数据
	 * @param privateKey 私钥
	 * @return 解密后的数据
	 * @throws Exception 异常信息
	 */
	public static String decryptByPrivateKey(String data, String privateKey) throws Exception {
		return decryptByPrivateKey(data, privateKey, "RSA/ECB/PKCS1Padding");
	}

	/**
	 * 私钥解密
	 *
	 * @param data       需要解密的数据
	 * @param privateKey 私钥
	 * @return 解密后的数据
	 * @throws Exception 异常信息
	 */
	public static String decryptByPrivateKeyByWx(String data, String privateKey) throws Exception {
		return decryptByPrivateKey(data, privateKey, "RSA/ECB/OAEPWITHSHA-1ANDMGF1PADDING");
	}

	/**
	 * 私钥解密
	 *
	 * @param data       需要解密的数据
	 * @param privateKey 私钥
	 * @param fillMode   填充模式
	 * @return 解密后的数据
	 * @throws Exception 异常信息
	 */
	public static String decryptByPrivateKey(String data, String privateKey, String fillMode) throws Exception {
		byte[] encryptedData = Base64.decode(data);
		byte[] keyBytes = Base64.decode(privateKey);
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
		Key key = keyFactory.generatePrivate(pkcs8KeySpec);
		Cipher cipher = Cipher.getInstance(fillMode);

		cipher.init(Cipher.DECRYPT_MODE, key);
		int inputLen = encryptedData.length;
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int offSet = 0;
		byte[] cache;
		int i = 0;
		// 对数据分段解密
		while (inputLen - offSet > 0) {
			if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
				cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
			} else {
				cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
			}
			out.write(cache, 0, cache.length);
			i++;
			offSet = i * MAX_DECRYPT_BLOCK;
		}
		byte[] decryptedData = out.toByteArray();
		out.close();
		return new String(decryptedData);
	}

	/**
	 * 从字符串中加载公钥
	 *
	 * @param publicKeyStr 公钥数据字符串
	 * @throws Exception 异常信息
	 */
	public static PublicKey loadPublicKey(String publicKeyStr) throws Exception {
		try {
			byte[] buffer = Base64.decode(publicKeyStr);
			KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
			X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
			return keyFactory.generatePublic(keySpec);
		} catch (NoSuchAlgorithmException e) {
			throw new Exception("无此算法");
		} catch (InvalidKeySpecException e) {
			throw new Exception("公钥非法");
		} catch (NullPointerException e) {
			throw new Exception("公钥数据为空");
		}
	}

	/**
	 * 从字符串中加载私钥<br>
	 * 加载时使用的是PKCS8EncodedKeySpec（PKCS#8编码的Key指令）。
	 *
	 * @param privateKeyStr 私钥
	 * @return {@link PrivateKey}
	 * @throws Exception 异常信息
	 */
	public static PrivateKey loadPrivateKey(String privateKeyStr) throws Exception {
		try {
			byte[] buffer = Base64.decode(privateKeyStr);
			PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);
			KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
			return keyFactory.generatePrivate(keySpec);
		} catch (NoSuchAlgorithmException e) {
			throw new Exception("无此算法");
		} catch (InvalidKeySpecException e) {
			throw new Exception("私钥非法");
		} catch (NullPointerException e) {
			throw new Exception("私钥数据为空");
		}
	}

	public static String getPrivateKeyStr(PrivateKey privateKey) {
		return Base64.encode(privateKey.getEncoded());
	}

	public static String getPublicKeyStr(PublicKey publicKey) {
		return Base64.encode(publicKey.getEncoded());
	}

	public static void main(String[] args) throws Exception {
		Map<String, String> keys = getKeys();
		String publicKey = keys.get("publicKey");
		String privateKey = keys.get("privateKey");
		String content = "我是Javen,I am Javen";
		String encrypt = encryptByPublicKey(content, publicKey);
		String decrypt = decryptByPrivateKey(encrypt, privateKey);
		System.out.println("加密之后：" + encrypt);
		System.out.println("解密之后：" + decrypt);

		System.out.println("======华丽的分割线=========");

		content = "我是Javen,I am Javen";
		encrypt = encryptByPublicKeyByWx(content, publicKey);
		decrypt = decryptByPrivateKeyByWx(encrypt, privateKey);
		System.out.println("加密之后：" + encrypt);
		System.out.println("解密之后：" + decrypt);

		//OPPO
		String sign = encryptByPrivateKey(content, privateKey);
		System.out.println("加密之后：" + sign);
		System.out.println(checkByPublicKey(content, sign, publicKey));
	}
}

效果图