You could try freezing the pyasn.1 package into your micropython port/firmware, that should free up enough memory and thanks for the post. It was quite helpful for my little project — connect an esp32 running micropython to Google IoT Core using a secure crypto-element for key storage and ‘JWT’ signing instead of the employing on-board flash chip. —

So, more options now https://github.com/nihalpasham/micropython_w_atecc608a_googleIotCoreAuth