Support for custom protected headers in t_cose_sign1_encode_parameters

[maxtropets]

Suggesting to extend t_cose_sign1_encode_parameters with custom parameters handling.

One of the possible options - a callback(ctx) to be called after setting base parameters, so users can add more custom fields.

[maxtropets]

Hi @laurencelundblade, could you please let me know if this's a valid suggestion?

We were researching means to pass more protected headers whilst working on microsoft/CCF#6445.

We ended up introducing a more complex signing code with encode_paremeters_.._ replaced(). However, if you think there're other (better) ways of dealing with this issue, we'll very much appreciate hearing your thoughts on this.

cc @achamayou

[laurencelundblade]

Hi,

The t_cose dev branch supports custom parameters in the t_cose_sign_sign interface. While there's a fair bit of work to do on the dev branch the parameters part is pretty stable. It works by passing in a linked list of header parameters you want added. It works for COSE_Sign, COSE_Sign1, COSE_Encrypt, COSE_Recipient...

Maybe you want counter signatures? My thought there was to use something specific to counter signatures rather the (simple) extended parameter mechanism in the dev branch.

While the dev branch is compatible with the main branch, a switch to the dev branch is possibly a big thing for you because the dev branch is a big expansion of functionality and is not as stable.

[maxtropets]

Thank you very much for your reply. We went with a workaround this time, but will track the progress of the dev branch for the future.

Maybe you want counter signatures? My thought there was to use something specific to counter signatures rather the (simple) extended parameter mechanism in the dev branch.

For our purposes we specifically needed to set custom parameters (more details on spec).