前言：

RSA属于非对称加密。所谓非对称加密，需要两个密钥：公钥 (publickey) 和私钥 (privatekey)。公钥和私钥是一对，如果用公钥对数据加密，那么只能用对应的私钥解密。如果用私钥对数据加密，只能用对应的公钥进行解密。因为加密和解密用的是不同的密钥，所以称为非对称加密。

废话不多说，上代码

/**
 * @description: RSA工具类
 * @author: JuZi
 * @create: 2023-08-25 10:30:14
 **/
@Slf4j
@Component
public class RsaUtil {

    private static final String KEY_ALGORITHM = "RSA";
    private static final int KEY_SIZE = 2048;//设置长度
    private static final String PUBLIC_KEY = "publicKey";
    private static final String PRIVATE_KEY = "privateKey";
    public static final String SIGNATURE_ALGORITHM = "SHA256withRSA";

    /**
     * 生成公、私钥
     * 根据需要返回String或byte[]类型
     *
     * @return
     */
    private static Map<String, String> createRSAKeys() {
        Map<String, String> keyPairMap = new HashMap<>();
        try {
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(KEY_ALGORITHM);
            keyPairGenerator.initialize(KEY_SIZE, new SecureRandom());
            KeyPair keyPair = keyPairGenerator.generateKeyPair();

            PublicKey publicKey = keyPair.getPublic();
            PrivateKey privateKey = keyPair.getPrivate();

            //获取公、私钥值
            String publicKeyValue = byte2Base64String(publicKey.getEncoded());
            String privateKeyValue = byte2Base64String(privateKey.getEncoded());

            //存入
            keyPairMap.put(PUBLIC_KEY, publicKeyValue);
            keyPairMap.put(PRIVATE_KEY, privateKeyValue);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return keyPairMap;
    }

    /**
     * 通过私钥对参数进行加密
     *
     * @param Data
     * @param privateKey
     * @return
     */
    public static String MakeSign(String Data, String privateKey) {
        try {
            byte[] data = Data.getBytes();
            byte[] keyBytes = base64String2Byte(privateKey);
            PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);

            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

            PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);
            //这个根据需求填充SHA1WithRSA或SHA256WithRSA
            Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
            signature.initSign(priKey);
            signature.update(data);
            return byte2Base64String(signature.sign());
        } catch (Exception e) {
            return "";
        }
    }

    /**
     * 使用公钥
     *
     * @param Data_ori
     * @param Singnature
     * @param publicKeyBase64Str
     * @return
     */
    public static boolean VeriSign(String Data_ori, String Singnature, String publicKeyBase64Str) {
        try {
            byte[] signed = base64String2Byte(Singnature);

            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(base64String2Byte(publicKeyBase64Str));
            KeyFactory keyFactory = null;
            keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            PublicKey publicKey = keyFactory.generatePublic(keySpec);
            //这个根据需求填充SHA1WithRSA或SHA256WithRSA
            Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
            signature.initVerify(publicKey);
            signature.update(Data_ori.getBytes(StandardCharsets.UTF_8));
            return signature.verify(signed);
        } catch (Exception e) {
            return false;
        }
    }

    /**
     * base64字符串转字节数组
     *
     * @param base64Str
     * @return
     */
    public static byte[] base64String2Byte(String base64Str) {
        return Base64.decodeBase64(base64Str);
    }

    /**
     * 字节数组转base64字符串
     *
     * @param bytes
     * @return
     */
    public static String byte2Base64String(byte[] bytes) {
        return new String(new Base64().encode(bytes));
    }

    public static byte charToByte(char c) {
        return (byte) "0123456789ABCDEF".indexOf(c);
    }
}

工具类全文如上所示，接下来看看效果

测试代码

public static void main(String[] args) throws Exception {
        log.info("-----开始生成公钥和私钥-----");
        Map<String, String> keys = createRSAKeys();
        log.info("-----公钥base64：{}-----", keys.get(PUBLIC_KEY));
        log.info("-----私钥base64：{}-----", keys.get(PRIVATE_KEY));

        log.info("-----开始对数据进行加密-----");
        String data = "hello word ！";
        log.info("-----源数据：{}-----", data);
        String sign = RsaUtil.MakeSign(data, keys.get(PRIVATE_KEY));
        log.info("-----私钥加密结果：{}-----", sign);

        log.info("-----开始用公钥对私钥的加密验证-----");
        log.info("-----公钥验证结果：{}-----", VeriSign(data, sign, keys.get(PUBLIC_KEY)));

    }