topic Re: How to read CSEc keys in S32K

How to read CSEc keys

xiongsl — Wed, 21 Feb 2024 04:40:24 GMT

Hello,

My software needs to support RSA2048, but the SDK doesn't support it yet.

If the key is stored to CSEc, how can I read the key so that the software can complete the digital signature?

Key length is 256 bytes.

Re: How to read CSEc keys

lukaszadrapa — Wed, 21 Feb 2024 06:35:00 GMT

Hi @xiongsl
SDK won't support RSA2048 because there's no such hardware feature on CSEc.
And there's no way to store such key to the CSEc. Nonvolatile keys can't be exported from CSEc. This would violate SHE specification. Only RAM key can be exported if plain key attribute is cleared.
So, the only option I can see in case of S32K1 device is to emulate this function by software (like wolfssl) and store the key in normal flash.
Regards,
Lukas

Re: How to read CSEc keys

xiongsl — Thu, 22 Feb 2024 02:27:22 GMT

Hi @lukaszadrapa

In other words, only the 16-byte key of RAM_KEY supports reading. KEY_01~KEY_17 does not support reading, so the RSA2048 key can only be stored in FLASH or EEPROM.
Regards,
xiongsl

Re: How to read CSEc keys

xiongsl — Thu, 22 Feb 2024 02:35:50 GMT

Can the attributes of KEY_01~KEY_17 be cleared and changed to something like RAM_KEY?

Re: How to read CSEc keys

lukaszadrapa — Thu, 22 Feb 2024 06:07:51 GMT

No, such changes can't be done in CSEc.

Re: How to read CSEc keys

xiongsl — Thu, 22 Feb 2024 06:12:01 GMT

Okay, thanks for the answer.