private static String base64UrlEncode(byte[] value) {
    return Base64
      .getUrlEncoder()
      .encodeToString(value)
      .replace('+', '-')
      .replace('/', '_')
      .replace("=", "");
  }

  public String sign(String data) {
    String res = "";
    try {
      Signature sig = Signature.getInstance("GOST3411_2012_256withGOST3410_2012_256", "JCSP");
      sig.initSign(this.key);
      sig.update(data.getBytes());

      res = base64UrlEncode(sig.sign());
    } catch(java.security.NoSuchAlgorithmException e) {
      e.printStackTrace();
    } catch(java.security.InvalidKeyException e) {
      e.printStackTrace();
    } catch(java.security.SignatureException e) {
      e.printStackTrace();
    } catch(java.security.NoSuchProviderException e) {
      e.printStackTrace();
    }

    return res;
  }