code: public static byte[] readKeyBytes(InputStream keyStream) {
  		PemObject pemObject = readPemObject(keyStream);
  		if (null != pemObject) {
  			return pemObject.getContent();
  		}
  		return null;
  	}
docs: 从pem文件中读取公钥或私钥
  
  @param keyStream pem流
  @return 密钥bytes
  @since 4.5.2