docs: public static byte[] generateSeed(String mnemonic, String passphrase) {
          if (isMnemonicEmpty(mnemonic)) {
              throw new IllegalArgumentException("Mnemonic is required to generate a seed");
          }
          passphrase = passphrase == null ? "" : passphrase;
  
          String salt = String.format("mnemonic%s", passphrase);
          PKCS5S2ParametersGenerator gen = new PKCS5S2ParametersGenerator(new SHA512Digest());
          gen.init(mnemonic.getBytes(UTF_8), salt.getBytes(UTF_8), SEED_ITERATIONS);
  
          return ((KeyParameter) gen.generateDerivedParameters(SEED_KEY_SIZE)).getKey();
      }