Hi @Eugene68!
As mentioned here, Mbed TLS is now maintained under open governance at TrustedFirmware.org
please post your questions there next time, if these are not Mbed OS or Pelion related.
It is better you don’t store it as an mbedtls_pk_context blob, as it also stores pointers to data in non persistent memory.
Have you considered using mbedtls_pk_write_key_der() which converts the context into its DER format?
Regards,
Mbed Support
Ron