code: public static CipherUtil buildInstance(PrivateKey privateKey, PublicKey publicKey) {
          return new AsymmetricCipher(new String(BASE_64.encrypt(privateKey.getEncoded())) + ":"
                                      + new String(BASE_64.encrypt(publicKey.getEncoded())),
              Algorithms.RSA, privateKey, publicKey);
      }
docs: 非对称加密构造器
  
  @param privateKey PKCS8格式的私钥
  @param publicKey  X509格式的公钥
  @return AsymmetricCipher