[Suit] My hackathon progress

[Ken Takayama <[e-mail]>]

Hi Hannes and SUIT team

Hi, I'm Ken Takayama, an implementer of SUIT Manifest parser,
and working with Hannes to add Firmware Encryption support.

For the first step to support COSE_Encrypt HPKE,
I added a data structure to represent multiple signing algorithms and
signatures,
and code that signs and verifies the SUIT_Authentication_Block.
It is not tested yet.
<https://github.com/yuichitk/libcsuit/tree/multiple-mechanisms-and-keys>

I did this task first because it is also required by HPKE which has
multiple algorithms.
Tomorrow morning, I will try to add code calls t_cose_encrypt_* functions
to encode Firmware Encrypted SUIT Manifest described by the data structure.


In today's hackathon, a question was came up to my mind:
SUIT_Authentication_Block can hold multiple signatures and macs,
but how can we validate it?
Option A) SUIT_Authentication_Block is valid if ALL of signatures and macs
are valid
Option B) SUIT_Authentication_Block is valid if ANY of signatures or macs
is valid
Option C) it depends on ACL (Access Control List)
This is related to the case when the SUIT_Authentication_Block has
COSE_Sign_Tagged signatures.

Ken