不再过多介绍， 依赖hutool库

加解密（hutool）

可通过new RSA()后获取密钥对（公钥、私钥）；定义为常量。rsa.encrypt()加密得到byte[]，

⚠：new String(byte[]);的方式导致输出乱码，致使后续解密ERROR；相关链接

通常通过 base64 对 byte[]进行编码；
然后通过rsa.decrypt() 对base64/byte[] 解密。

  1. import cn.hutool.core.codec.Base64;
  2. import cn.hutool.crypto.asymmetric.KeyType;
  3. import cn.hutool.crypto.asymmetric.RSA;
  5. public class RsaTest {
  7.     private final static String PUBLIC_KEY = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC05MBh04Wgw7S4xPn/PRo2QKFS70G4mkEzn5kibeN81Q/WuG4lJaWE6wW65hsFuz/DxRHvZaCeEO82ebr5LefYRzRXRzq6/a03e2wxiSA3DyFIcqySro+UpKDx824FfVIi+fs54Wc5xATThFKbfVD4UUA3hgAiq5sQpRpqq3CvTQIDAQAB";
  8.     private final static String PRIVATE_KEY = "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";
  10.     public static void main(String[] args) {
  11.         RSA rsa = new RSA(PRIVATE_KEY, PUBLIC_KEY);
  12.         byte[] encrypt = rsa.encrypt("username:password", KeyType.PublicKey);
  13.         String base64 = Base64.encode(encrypt);
  14.         System.out.println("base64 = " + base64);
  15.         //new String(byte[]); 的方式导致输出乱码，且在解密时ERROR；
  16.         //https://blog.csdn.net/qq_38022877/article/details/88560518
  18.         //方式一、byte[] decrypt = rsa.decrypt(encrypt, KeyType.PrivateKey);
  19.         //方式二、
  20.         byte[] decrypt = rsa.decrypt(base64, KeyType.PrivateKey);
  21.         String s1 = new String(decrypt);
  22.         System.out.println("s1 = " + s1);
  23.     }
  24. }

工具类（生成密钥对到文件）

  1. package utils;
  3. import java.io.File;
  4. import java.io.IOException;
  5. import java.nio.file.Files;
  6. import java.security.*;
  7. import java.security.spec.InvalidKeySpecException;
  8. import java.security.spec.PKCS8EncodedKeySpec;
  9. import java.security.spec.X509EncodedKeySpec;
  10. import java.util.Base64;
  13. public class RsaUtils {
  15.     private static final int DEFAULT_KEY_SIZE = 2048;
  16.     /**
  17.      * 从文件中读取公钥
  18.      *
  19.      * @param filename 公钥保存路径，相对于classpath
  20.      * @return 公钥对象
  21.      * @throws Exception
  22.      */
  23.     public static PublicKey getPublicKey(String filename) throws Exception {
  24.         byte[] bytes = readFile(filename);
  25.         return getPublicKey(bytes);
  26.     }
  28.     /**
  29.      * 从文件中读取密钥
  30.      *
  31.      * @param filename 私钥保存路径，相对于classpath
  32.      * @return 私钥对象
  33.      * @throws Exception
  34.      */
  35.     public static PrivateKey getPrivateKey(String filename) throws Exception {
  36.         byte[] bytes = readFile(filename);
  37.         return getPrivateKey(bytes);
  38.     }
  40.     /**
  41.      * 获取公钥
  42.      *
  43.      * @param bytes 公钥的字节形式
  44.      * @return
  45.      * @throws Exception
  46.      */
  47.     private static PublicKey getPublicKey(byte[] bytes) throws Exception {
  48.         bytes = Base64.getDecoder().decode(bytes);
  49.         X509EncodedKeySpec spec = new X509EncodedKeySpec(bytes);
  50.         KeyFactory factory = KeyFactory.getInstance("RSA");
  51.         return factory.generatePublic(spec);
  52.     }
  54.     /**
  55.      * 获取密钥
  56.      *
  57.      * @param bytes 私钥的字节形式
  58.      * @return
  59.      * @throws Exception
  60.      */
  61.     private static PrivateKey getPrivateKey(byte[] bytes) throws NoSuchAlgorithmException, InvalidKeySpecException {
  62.         bytes = Base64.getDecoder().decode(bytes);
  63.         PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(bytes);
  64.         KeyFactory factory = KeyFactory.getInstance("RSA");
  65.         return factory.generatePrivate(spec);
  66.     }
  68.     /**
  69.      * 根据密文，生成rsa公钥和私钥,并写入指定文件
  70.      *
  71.      * @param publicKeyFilename  公钥文件路径
  72.      * @param privateKeyFilename 私钥文件路径
  73.      * @param secret             生成密钥的密文
  74.      */
  75.     public static void generateKey(String publicKeyFilename, String privateKeyFilename, String secret, int keySize) throws Exception {
  76.         KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
  77.         SecureRandom secureRandom = new SecureRandom(secret.getBytes());
  78.         keyPairGenerator.initialize(Math.max(keySize, DEFAULT_KEY_SIZE), secureRandom);
  79.         KeyPair keyPair = keyPairGenerator.genKeyPair();
  80.         // 获取公钥并写出
  81.         byte[] publicKeyBytes = keyPair.getPublic().getEncoded();
  82.         publicKeyBytes = Base64.getEncoder().encode(publicKeyBytes);
  83.         writeFile(publicKeyFilename, publicKeyBytes);
  84.         // 获取私钥并写出
  85.         byte[] privateKeyBytes = keyPair.getPrivate().getEncoded();
  86.         privateKeyBytes = Base64.getEncoder().encode(privateKeyBytes);
  87.         writeFile(privateKeyFilename, privateKeyBytes);
  88.     }
  90.     private static byte[] readFile(String fileName) throws Exception {
  91.         return Files.readAllBytes(new File(fileName).toPath());
  92.     }
  94.     private static void writeFile(String destPath, byte[] bytes) throws IOException {
  95.         File dest = new File(destPath);
  96.         if (!dest.exists()) {
  97.             dest.createNewFile();
  98.         }
  99.         Files.write(dest.toPath(), bytes);
  100.     }
  101. }