Description
This issue refers to the security review requested in this issue w3c/security-request#55.
In section 5.4, about cryptographic layering (employment of multiple different algorithms at same time to survive failures of one or more cryptographic algorithms without losing the protection). This mechanism is useful for this historical moment when hybrid post-quantum solutions (use of classical primitives and post-quantum primitives) are recommended. For what I'm concerned, crypto layering is particularly useful for hybrid post-quantum solutions and I don't see any other reason to use different classical algorithms to sign same data. So, suggest to better explain post-quantum topic (the need to have 2 different digital signatures, one classical and the other post-quantum).
In addition to that, might be useful to point out differences on concatenation of more signatures (chain signatures) and two or more separate digital signatures of same data (set signatures). On the one hand, signature of signature of data, on the other hand two signatures of same data, which is different. The choice between the two mechanisms could lead to implementation challenges and therefore requires some considerations and special attention to the size of the data processed (including signatures) and the structure to be given to them. So suggest explaining topic and pay attention to this concept.
SING discussed this topic during the meeting SING_2025-04-01 and it turned out that we don't want to specify which of the two mechanisms to use but it might be helpful to explain the topic.